Liquid Crystal Display And Method For Manufacturing The Same

ABSTRACT

A liquid crystal display includes a pair of substrates and a liquid crystal layer interposed between the substrates and has a reflective area and a transmissive area. At least one of the substrates is provided with a retardation film whose phase difference differs between the reflective area and the transmissive area. Alternatively, at least one of the substrates is provided with a retardation film whose slow axis differs between the reflective area and the transmissive area.

RELATED APPLICATION DATA

This application is a divisional of U.S. patent application Ser. No.10/714,133, filed Nov. 14, 2003, which is incorporated herein byreference to the extent permitted by law. This application claims thebenefit of priority to Japanese Patent Application No. JP2002-333364,filed Nov. 18, 2002, and Japanese Patent Application JP2002-049163,filed Feb. 26, 2002, which also are incorporated herein by reference tothe extent permitted by law.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a transflective liquid crystal displayhaving features of both reflective and transmissive displays and amethod for manufacturing the transflective liquid crystal display.

2. Description of the Related Art

In general, transmissive liquid crystal displays using backlights fordisplaying images have been mainly used as displays for personalcomputers. Recently, however, there have been increasing demands fordisplays for mobile electronic devices such as personal digitalassistants (PDAs) and mobile phones, and reflective liquid crystaldisplays which consume less power than the transmissive liquid crystaldisplays have been attracting attention. In the reflective liquidcrystal displays, ambient light incident on and reflected by a reflectoris used for displaying images, so no backlight is necessary and powerconsumption is low. Therefore, electronic devices including thereflective liquid crystal displays can be operated for a longer timecompared to those including the transmissive liquid crystal displays.

For the case in which the reflective liquid crystal displays, whichnormally use ambient light for displaying images, are used in darkplaces, a construction has been proposed in which a front light isarranged on a display side, that is, on the front of a liquid crystalpanel and light emitted from the front light is used for displayingimages. However, when the front light is disposed on the display side ofthe panel, the reflectivity and the contrast decrease and the imagequality degrades.

In order to solve this problem, transflective liquid crystal displays inwhich a reflector has a transmissive area in a pixel area and which havefeatures of both the reflective and transmissive liquid crystal displayshave been developed. In the transflective liquid crystal displays, abacklight is arranged on a liquid crystal panel on the side opposite tothe display side, so that sufficient visibility can be obtained in bothdark and light places without degrading the image quality as areflective display. Accordingly, high image quality can be obtained. Thebasic construction of the transflective liquid crystal displays isdisclosed in, for example, Japanese Unexamined Patent ApplicationPublications Nos. 2000-29010 and 2000-35570.

With reference to FIG. 27, in a known transflective liquid crystaldisplay 101, a reflective electrode 104 composed of a material with highreflectivity and a transparent electrode 105 composed of a material withhigh transmittance are provided on a main surface of a substrate 102,the reflective electrode 104 being laminated on the substrate 102 withan interlayer film 103 therebetween, and a quarter-wavelength layer(hereinafter called a λ/4 layer) 106 and a polarizer 107 are laminatedon the other main surface of the substrate 102 in that order. Inaddition, in the liquid crystal display 101, a counter electrode 109 isprovided on a main surface of another substrate 108 on the side facingthe substrate 102, and a λ/4 layer 110 and a polarizer 111 are laminatedon the other main surface of the substrate 108 in that order. A liquidcrystal layer 112 composed of a liquid crystal material is interposedbetween the reflective electrode 104 and the counter electrode 109 andbetween the transparent electrode 105 and the counter electrode 109.Thus, the liquid crystal display 101 shown in FIG. 27 includes tworetardation layers, one on the front and one on the back.

In order to reliably suppress the influence of chromatic dispersion andimprove the dark state display, the construction shown in FIG. 28 mayalso be used. In a liquid crystal display 201 shown in FIG. 28, a λ/4layer 106 and a half-wavelength layer (hereinafter called a λ/2 layer)113 provided on a substrate 102 are used in combination with each otherand a λ/4 layer 110 and a λ/2 layer 114 provided on a substrate 108 areused in combination with each other. Thus, four retardation layers areused in total.

In the liquid crystal display 101 shown in FIG. 27, the λ/4 layer 110which serves as a retardation layer is provided on the display side ofthe substrate 108 such that it covers the entire area of the substrate108 in order to suppress the influence of chromatic dispersion andachieve reflective display. Therefore, although a retardation layer suchas a λ/4 layer is not necessary for transmissive display, since the λ/4layer 110 which is provided on the display side for achieving reflectivedisplay covers the entire area of the substrate 108, the λ/4 layer 106must be provided on the substrate 102 arranged on the back in order tocompensate for the phase difference of the λ/4 layer 110. Morespecifically, since a retardation layer is provided on the display sidefor achieving reflective display even though it is not necessary fortransmissive display, an additional retardation layer must be providedto compensate for the phase difference of the retardation layer arrangedon the display side.

Similarly, in the liquid crystal display 201 shown in FIG. 28, two ofthe four retardation layers which are placed on the back are simplyprovided to compensate for the phase difference of the other tworetardation layers used for reflective display, and are not necessaryfor transmissive display.

As described above, in known transflective liquid crystal displays, therequired number of retardation layers is large compared to thereflective liquid crystal displays and the transmissive liquid crystaldisplays. Accordingly, high costs are incurred and the cell thickness islarge.

SUMMARY OF THE INVENTION

Accordingly, in order to solve the above-described problems, an objectof the present invention is to provide a transflective liquid crystaldisplay which requires only a small number of retardation layers to bedisposed on, for example, the back and a method for manufacturing theliquid crystal display.

In order to attain the above-described object, according to the presentinvention, a liquid crystal display includes a pair of substrates and aliquid crystal layer interposed between the substrates and has areflective area and a transmissive area, and at least one of thesubstrates is provided with a retardation film whose phase differencediffers between the reflective area and the transmissive area.

According to another aspect of the present invention, a method formanufacturing a liquid crystal display which has a pair of substratesand a liquid crystal layer interposed between the substrates and whichhas a reflective area and a transmissive area includes the steps offorming a retardation film on at least one of the substrates andpatterning the retardation film such that the retardation film remainsat least in the reflective area and the phase difference of theretardation film differs between the reflective area and thetransmissive area.

According to the liquid crystal display having the above-describedconstruction, the phase difference of the retardation film provided onone of the substrates differs between the reflective area and thetransmissive area, and the retardation film, which is necessary fordisplaying images in the reflective area, does not function in thetransmissive area. Accordingly, sufficient reflectivity can be obtainedin the reflective area due to the function of the retardation film andtransmissive display can be achieved in the transmissive area withoutproviding an additional retardation layer to compensate for the phasedifference of the retardation layer.

According to another aspect of the present invention, a liquid crystaldisplay includes a pair of substrates and a liquid crystal layerinterposed between the substrates and has a reflective area and atransmissive area, and at least one of the substrates is provided with aretardation film whose slow axis differs between the reflective area andthe transmissive area.

In addition, according to another aspect of the present invention, amethod for manufacturing a liquid crystal display which has a pair ofsubstrates and a liquid crystal layer interposed between the substratesand which has a reflective area and a transmissive area includes thestep of forming a retardation film whose slow axis is different betweenthe reflective area and the transmissive area on at least one of thesubstrates.

According to the liquid crystal display having the above-describedconstruction, the slow axis of the retardation film provided on one ofthe substrates differs between the reflective area and the transmissivearea, and the retardation film, which is necessary for displaying imagesin the reflective area, does not function in the transmissive area.Accordingly, sufficient reflectivity can be obtained in the reflectivearea due to the function of the retardation film and transmissivedisplay can be achieved in the transmissive area without providing anadditional retardation layer to compensate for the phase difference ofthe retardation layer.

In the known transflective liquid crystal displays, a circular polarizercan be obtained by combining a polarizer and a λ/4 layer obtained by asingle rubbing process and an exposure process, and the opticalconstruction can therefore be easily designed. However, as describedabove, a relatively large number of retardation films are necessary andhigh costs are incurred. On the contrary, according to the presentinvention, retardation films necessary in the known construction can beomitted by providing a retardation layer whose phase difference differsbetween the transmissive area and the reflective area and optimizing therelationship between the rubbing direction of the retardation film andthe transmission axis of the polarizer.

In addition, in the liquid crystal display of the present invention,images can be displayed in a twisted nematic mode, which is used inknown transmissive liquid crystal displays, in the transmissive area.Accordingly, the contrast can be increased in transmissive display. Inaddition, in the reflective area, images can be displayed in anelectrically controlled birefringence (ECB) mode where a twist angle isthe same as or different from that in the transmissive area.Accordingly, the allowance for the cell gap increases, which leads tobetter productivity.

Accordingly, the present invention provides a transflective liquidcrystal display which requires only a small number of retardation filmsand has a small cell thickness, and which can be manufactured at lowcosts.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing the basic construction of aliquid crystal display according to a first embodiment of the presentinvention;

FIG. 2 is an exploded perspective view showing the optical constructionof the liquid crystal display shown in FIG. 1 when no voltage isapplied;

FIG. 3 is an exploded perspective view showing the optical constructionof the liquid crystal display shown in FIG. 1 when a voltage is applied;

FIG. 4 is a schematic sectional view showing a modification of theliquid crystal display according to the first embodiment;

FIG. 5 is a schematic sectional view showing another modification of theliquid crystal display according to the first embodiment;

FIG. 6 is a schematic sectional view showing another modification of theliquid crystal display according to the first embodiment;

FIGS. 7A to 7C are diagrams showing the basic construction of a liquidcrystal display according to a second embodiment of the presentinvention;

FIG. 8 is an exploded perspective view showing the optical constructionof the liquid crystal display shown in FIGS. 7A to 7C when no voltage isapplied;

FIG. 9 is an exploded perspective view showing the optical constructionof the liquid crystal display shown in FIGS. 7A to 7C when a voltage isapplied;

FIGS. 10A to 10C are diagrams showing a modification of the liquidcrystal display according to the second embodiment;

FIGS. 11A to 11C are diagrams showing another modification of the liquidcrystal display according to the second embodiment;

FIG. 12 is a schematic sectional view showing the basic construction ofa liquid crystal display according to a third embodiment of the presentinvention;

FIG. 13 is an exploded perspective view showing the optical constructionof the liquid crystal display shown in FIG. 12 when no voltage isapplied;

FIG. 14 is an exploded perspective view showing the optical constructionof the liquid crystal display shown in FIG. 12 when a voltage isapplied;

FIG. 15 is a schematic sectional view showing a modification of theliquid crystal display according to the third embodiment;

FIG. 16 is a schematic sectional view showing another modification ofthe liquid crystal display according to the third embodiment;

FIG. 17 is a schematic sectional view showing another modification ofthe liquid crystal display according to the third embodiment;

FIGS. 18A to 18C are diagrams showing the basic construction of a liquidcrystal display according to a fourth embodiment of the presentinvention;

FIG. 19 is an exploded perspective view showing the optical constructionof the liquid crystal display shown in FIGS. 18A to 18C when no voltageis applied;

FIG. 20 is an exploded perspective view showing the optical constructionof the liquid crystal display shown in FIGS. 18A to 18C when a voltageis applied;

FIGS. 21A to 21C are diagrams showing a modification of the liquidcrystal display according to the fourth embodiment;

FIG. 22 is a schematic sectional view showing another modification ofthe liquid crystal display according to the fourth embodiment;

FIG. 23 is a schematic sectional view showing another modification ofthe liquid crystal display according to the fourth embodiment;

FIGS. 24A to 24C are diagrams showing another modification of the liquidcrystal display according to the fourth embodiment;

FIGS. 25A to 25C are diagrams showing another modification of the liquidcrystal display according to the fourth embodiment;

FIG. 26 is a sectional view of a substrate arranged on the back which isprovided with TFTs;

FIG. 27 is a schematic sectional view of a known transflective liquidcrystal display having two retardation layers; and

FIG. 28 is a schematic sectional view of a known transflective liquidcrystal display having four retardation layers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Liquid crystal displays to which the present invention is applied andmethods for manufacturing the liquid crystal displays will be describedbelow with reference to the accompanying drawings.

First Embodiment

A transflective liquid crystal display according to a first embodimentof the present invention will be described below. The liquid crystaldisplay according to the first embodiment is characterized in that thephase difference of a retardation layer is different between areflective area and a transmissive area. The basic construction of theliquid crystal display according to the first embodiment will bedescribed below with reference to FIG. 1.

In a liquid crystal display 1 shown in FIG. 1, a reflective electrode 3composed of a material with high reflectivity which defines a reflectivearea and a transparent electrode 4 composed of a material with hightransmittance which defines a transmissive area are provided on a mainsurface of a substrate 2, and a polarizer 5 is provided on the othermain surface of the substrate 2. In addition, another substrate 6 whichreceives ambient light is placed on the display side, and areflective-area λ/4 layer 7 which serves as a retardation layer andcovers the reflective area and a counter electrode 8 which covers boththe reflective and transmissive areas are provided on a main surface ofthe substrate 6 which faces the substrate 2. In addition, a polarizer 9is provided on the other main surface of the substrate 6. A liquidcrystal layer 10 composed of a liquid crystal material is interposedbetween the substrate 2 and the substrate 6, and a backlight (not shown)for transmissive display is disposed on the outer side of the polarizer5. The transmission axis of the polarizer 9 and that of the polarizer 5are perpendicular to each other. In addition, the slow axis of thereflective-area λ/4 layer 7 which serves as the retardation layer is ata predetermined angle with respect to the transmission axis or theabsorption axis of the polarizer 9 (45° with respect to the transmissionaxis in the present embodiment).

In the liquid crystal display 1 according to the first embodiment, thereflective-area λ/4 layer 7 which serves as the retardation layer isprovided only in the reflective area, and is not provided in thetransmissive area. Accordingly, a phase difference is different betweenthe reflective area and the transmissive area. More specifically, aphase difference necessary for reflective display is obtained due to thefunction of the reflective-area λ/4 layer 7 in the reflective area,whereas no phase difference occurs in the transmissive area. Accordingto the above-described construction, transmissive display can beachieved without providing an additional λ/4 layer on the back tocompensate for the phase difference of the reflective-area λ/4 layer 7provided on the display side.

The reflective-area λ/4 layer 7 which serves as the retardation layermay also be disposed on the outer side of the substrate 6. However, itis preferably disposed on the surface facing the liquid crystal layer10, as shown in FIG. 1, so that the problem of parallax caused by thethickness of the substrate 6 can be reduced.

The reflective-area λ/4 layer 7 which serves as the retardation layer isobtained by, for example, applying a liquid-crystal polymer to thesubstrate 6 after an alignment process, such as rubbing, and forming apattern such that the liquid-crystal polymer remains only in thereflective area. More specifically, a photosensitive liquid-crystalpolymer is applied to the substrate 6 after the alignment process, andan exposure process and a development process are performed so as toobtain the retardation layer having a desired pattern. Alternatively,the retardation layer may also be obtained by applying anultraviolet-curable liquid crystal monomer in a nematic phase to thesubstrate 6 or an alignment film and irradiating it with an ultravioletlight to grow a liquid-crystal polymer. The phase difference of theretardation layer can be arbitrarily adjusted by changing the thicknessthereof. The retardation layer is not necessarily composed of aliquid-crystal polymer, and may also be composed of, for example, anoriented film.

The operation of displaying an image on the liquid crystal display 1shown in FIG. 1 will be described below with reference to FIGS. 2 and 3.For convenience, the substrate 2 and the counter electrode 8 are omittedin FIGS. 2 and 3. The phase difference of the liquid crystal layer 10 isadjusted to be λ/4, where λ is the wavelength of light, in thereflective area and λ/2 in the transmissive area when light passesthrough the liquid crystal layer 10 once while no voltage is appliedthereto. When no voltage is applied, the liquid-crystal orientation isapproximately parallel to the substrates 2 and 6, is parallel to thealignment direction of the reflective-area λ/4 layer 7, and is at anangle of 45° with respect to the transmission axis of the polarizer 9.

A case in which no voltage is applied to the liquid crystal layer 10 andthe light state is obtained will be described below with reference toFIG. 2.

In the reflective area, ambient light is incident from the outer side ofthe substrate 6 (from the display side) and passes through the polarizer9, where it is linearly polarized in a direction parallel to thetransmission axis of the polarizer 9. The linearly polarized light isconverted into circularly polarized light as it passes through thereflective-area λ/4 layer 7, is converted into linearly polarized lightby the liquid crystal layer 10, and reaches the reflective electrode 3.The linearly polarized light is reflected by the reflective electrode 3so that the traveling direction thereof is reversed, and is convertedinto circularly polarized light as it passes through the liquid crystallayer 10 again. The circularly polarized light passes through thereflective-area λ/4 layer 7 again, where it is linearly polarized in thedirection parallel to the transmission axis of the polarizer 9, andpasses through the polarizer 9.

In the transmissive area, light emitted from the backlight is incidentfrom the outer side of the substrate 2 (from the back) and passesthrough the polarizer 5, where it is linearly polarized in a directionparallel to the transmission axis of the polarizer 5. The linearlypolarized light passes through the liquid crystal layer 10 having thephase difference of λ/2, where it is linearly polarized in a directionperpendicular to the transmission axis of the polarizer 5, that is, inthe direction parallel to the transmission axis of the polarizer 9, andpasses through the polarizer 9.

Next, a case in which a voltage is applied to the liquid crystal layer10 and the dark state is obtained will be described below with referenceto FIG. 3.

In the reflective area, ambient light is incident from the display sideand passes through the polarizer 9, where it is linearly polarized inthe direction parallel to the transmission axis of the polarizer 9. Thelinearly polarized light is converted into circularly polarized light asit passes through the reflective-area λ/4 layer 7. The circularlypolarized light passes through the liquid crystal layer I0 and reachesthe reflective electrode 3 without changing the polarization statethereof, and is reflected by the reflective electrode 3. When thecircularly polarized light is reflected by the reflective electrode 3,the rotating direction thereof is reversed. The thus reflectedcircularly polarized light passes through the liquid crystal layer 10again, is incident on the reflective-area λ/4 layer 7, where it islinearly polarized in a direction perpendicular to the transmission axisof the polarizer 9, and is absorbed by the polarizer 9.

In the transmissive area, light emitted from the backlight is incidentfrom the back and passes through the polarizer 5, where it is linearlypolarized in the direction parallel to the transmission axis of thepolarizer 5. The linearly polarized light passes through the liquidcrystal layer I0 and reaches the polarizer 9 without changing thepolarization state thereof, and is absorbed by the polarizer 9.

As described above, the reflective-area λ/4 layer 7, which is necessaryfor the dark state display in the reflective area, is not provided inthe transmissive area. Accordingly, sufficient reflectivity can beobtained in the reflective area due to the function of thereflective-area λ/4 layer 7 and transmissive display can be achieved inthe transmissive area without providing an additional retardation layeron the back to compensate for the phase difference of the retardationlayer on the display side. Accordingly, high quality, high contrastimages can be displayed in both reflective display and transmissivedisplay. In addition, it is not necessary to provide an additionalretardation layer on the back, so that the cell thickness can be reducedand costs can be reduced by the amount corresponding to the omittedretardation layer.

In the above description, liquid-crystal molecules in the liquid crystallayer are oriented approximately perpendicular to the substrates when avoltage is applied, and the liquid crystal layer has a phase differenceof λ/4 in the reflective area and λ/2 in the transmissive area when novoltage is applied. According to the present invention, however, theconstruction of the liquid crystal display may also be opposite. Morespecifically, the liquid crystal layer may also have a phase differenceof λ/4 in the reflective area and λ/2 in the transmissive area when avoltage is applied.

According to the present embodiment, the retardation layer is notlimited to that having a single-layer structure consisting of thereflective-area λ/4 layer, and may also have a two-layer structureconsisting of a reflective-area λ/4 layer and an additional retardationlayer which compensates for the chromatic dispersion of thereflective-area λ/4 layer. A case in which a λ/2 layer is provided asthe retardation layer which compensates for the chromatic dispersion ofthe reflective-area λ/4 layer will be described below with reference toFIG. 4. In FIG. 4, components similar to those of the liquid crystaldisplay 1 shown in FIG. 1 are denoted by the same reference numerals,and explanations thereof are thus omitted.

In a liquid crystal display 21 according to this modification, aretardation layer having a two-layer structure consisting of areflective-area λ/2 layer 22 and a reflective-area λ/4 layer 7 isprovided in the reflective area, and no retardation layer is provided inthe transmissive area.

As described above, in the liquid crystal display 21, the retardationlayer having a two-layer structure is provided in the reflective area.Accordingly, in addition to the effects obtained by the liquid crystaldisplay 1 having the basic structure, light leakage caused by thechromatic dispersion in the dark state display can be eliminated over awide wavelength range and the image quality can be improved.

In the above-described liquid crystal displays 1 and 21, the retardationlayer is completely removed in the transmissive area. According to thepresent invention, however, a retardation layer whose phase differenceis different from that of the retardation layer provided in thereflective area may also be provided in the transmissive area. A liquidcrystal display according to this modification will be described belowwith reference to FIG. 5. In FIG. 5, components similar to those of theliquid crystal display 1 shown in FIG. 1 and those of the liquid crystaldisplay 21 shown in FIG. 4 are denoted by the same reference numerals,and explanations thereof are thus omitted.

A liquid crystal display 31 shown in FIG. 5 is different from the liquidcrystal display 21 shown in FIG. 4 in that a transmissive-arearetardation layer 32 is provided on a substrate 6 on the side facing aliquid crystal layer 10. The phase difference of the transmissive-arearetardation layer 32 is determined by taking various characteristics ofthe liquid crystal layer 10 into account, and is preferably set suchthat a residual phase difference which occurs when sufficient voltage isapplied to the liquid crystal layer 10 can be canceled.

Accordingly, in the liquid crystal display 31, in addition to theeffects obtained by the above-described liquid crystal display 21, thedarkness in the dark state display can be increased in the transmissivearea and the image quality can be improved.

In this modification, a retardation layer having a two-layer structureconsisting of a reflective-area λ/4 layer 7 and a reflective-area λ/2layer 22 is provided in the reflective area. However, the effectsobtained by providing the transmissive-area retardation layer 32 canalso be obtained when a retardation layer having a single-layerstructure is provided in the reflective area.

According to the present embodiment, the liquid crystal display may alsobe a full-color liquid crystal display, as shown in FIG. 6.

In a liquid crystal display 41 shown in FIG. 6, color filters 42R, 42G,and 42B corresponding to red, green, and blue dots, respectively, areprovided on a substrate 6 on the side facing a liquid crystal layer 10.In addition, reflective-area λ/4 layers 7R, 7CA and 7B which serve asretardation layers are provided on the color filters 42R, 42G, and 42B,respectively, at regions corresponding to the reflective area. Inaddition, a counter electrode 8 is provided on these reflective-arearetardation layers with an overcoat layer 43 therebetween.

In the liquid crystal display 41 according to this modification, thethicknesses of the reflective-area λ/4 layers 7R, 7G, and 7B which serveas the retardation layers are adjusted in accordance with thetransmission wavelengths of the color filters 42R, 42CA and 42B,respectively, so that each retardation layer has a phase difference ofλ/4. Accordingly, the influence of the chromatic dispersion of eachcolor can be reduced and the image quality can be improved.

In the above descriptions, liquid crystal displays in which theretardation layer is provided on the substrate arranged on the displayside are explained. However, the present invention is not limited tothis, and is applicable as long as a retardation layer whose phasedifference is different between the reflective area and the transmissivearea is provided on at least one of the substrates. For example, thepresent invention may also be applied to a case where the retardationlayer is provided on the substrate adjacent to the backlight.

Second Embodiment

A transflective liquid crystal display according to a second embodimentof the present invention will be described below. The liquid crystaldisplay according to the second embodiment is similar to that of thefirst embodiment except for the orientation of the liquid crystal layer,that is, the orientation of the liquid-crystal molecules or theliquid-crystal orientation, in the reflective area and the transmissivearea. The basic construction of the liquid crystal display according tothe second embodiment will be described below with reference to FIGS. 7Ato 7C. In the figures, components similar to those of the liquid crystaldisplay 1 shown in FIG. 1 are denoted by the same reference numerals,and explanations thereof are thus omitted. FIG. 7C shows a schematicsectional view of the main part of a liquid crystal display 1′, andFIGS. 7A and 7B show the optical constructions in a reflective area anda transmissive area, respectively, of the liquid crystal display 1′. InFIGS. 7A and 7B and the following figures which show the opticalconstructions, the liquid-crystal orientation on the side facing asubstrate 6 is denoted by 10 t and the liquid-crystal orientation on theside facing a substrate 2 is denoted by 10 b. In addition, thetransmission axes of polarizers 5 and 9 are denoted by 5 a and 9 a,respectively.

With reference to FIGS. 7A to 7C, in the liquid crystal display 1′, theliquid-crystal orientations 10 t and 10 b in the reflective area are setsimilarly to, for example, those of the liquid crystal display 1 shownin FIG. 1. More specifically, when no voltage is applied to a liquidcrystal layer 10′, the liquid-crystal orientations 10 t and 10 b in thereflective area are parallel to the substrates 2 and 6 and are at anangle of 45° with respect to the transmission axes of the polarizers 5and 9. In addition, similar to the liquid crystal display 1 shown inFIG. 1, the liquid crystal layer 10′ in the reflective area is adjustedsuch that the phase difference is λ/4 when light passes through theliquid crystal layer 10′ once while no voltage is applied thereto.

In the transmissive area, the liquid-crystal orientation 10 t on theside facing the substrate 6 is parallel to the transmission axis 9 a ofthe polarizer 9 and the liquid-crystal orientation 10 b on the sidefacing the substrate 2 is parallel to the transmission axis 5 a of thepolarizer 5, so that a 90° twisted nematic state where theliquid-crystal molecules are twisted by 90° is obtained, when no voltageis applied to the liquid crystal layer 10′.

When a voltage is applied to the liquid crystal layer 10′, theliquid-crystal molecules are aligned approximately perpendicular to thesubstrates 2 and 6 in both the reflective area and the transmissivearea.

Accordingly, in the liquid crystal display 1′, the alignment directionsof alignment films (not shown) disposed between the substrates 2 and 6so as to face the liquid crystal layer 10′ are set as described below.That is, in the reflective area, the alignment directions of thealignment films adjacent to the substrates 2 and 6 are at an angle of45° with respect to the transmission axes 5 a and 9 a of the polarizers5 and 9, respectively. Accordingly, the alignment directions of thealignment films may either be at an angle of 90° with respect to theslow axis 7 a of a reflective-area λ/4 layer 7, as shown in FIG. 7A, orbe parallel to the slow axis 7 a of the reflective-area λ/4 layer 7. Inthe transmissive area, the alignment direction of the alignment filmadjacent to the substrate 2 is parallel to the transmission axis 5 a ofthe polarizer 5, and the alignment direction of the alignment filmadjacent to the substrate 6 is parallel to the transmission axis 9 a ofthe polarizer 9.

The operation of displaying an image on the liquid crystal display 1′shown in FIGS. 7A to 7C will be described below with reference to FIGS.8 and 9. For convenience, the substrate 2, a counter electrode 8, andthe alignment films facing the liquid crystal layer 10′ are omitted inFIGS. 8 and 9.

A case in which no voltage is applied to the liquid crystal layer 10′and the light state is obtained will be described below with referenceto FIG. 8.

In the reflective area, ambient light is incident from the outer side ofthe substrate 6 (from the display side) and passes through the polarizer9, where it is linearly polarized in a direction parallel to thetransmission axis of the polarizer 9. The linearly polarized light isconverted into circularly polarized light as it passes through thereflective-area λ/4 layer 7, is converted into linearly polarized lightby the liquid crystal layer 10′, and reaches a reflective electrode 3.The linearly polarized light is reflected by the reflective electrode 3so that the traveling direction thereof is reversed, and is convertedinto circularly polarized light as it passes through the liquid crystallayer 10′ again. The circularly polarized light passes through thereflective-area λ/4 layer 7 again, where it is linearly polarized in thedirection parallel to the transmission axis of the polarizer 9, andpasses through the polarizer 9.

In the transmissive area, light emitted from a backlight is incidentfrom the outer side of the substrate 2 (from the back) and passesthrough the polarizer 5, where it is linearly polarized in a directionparallel to the transmission axis of the polarizer 5. The linearlypolarized light passes through the liquid crystal layer 10′ in the 90°twisted nematic state, where it is linearly polarized in a directionperpendicular to the transmission axis of the polarizer 5, that is, inthe direction parallel to the transmission axis of the polarizer 9, andpasses through the polarizer 9.

Next, a case in which a voltage is applied to the liquid crystal layer10′ and the dark state is obtained will be described below withreference to FIG. 9.

In the reflective area, ambient light is incident from the display sideand passes through the polarizer 9, where it is linearly polarized inthe direction parallel to the transmission axis of the polarizer 9. Thelinearly polarized light is converted into circularly polarized light asit passes through the reflective-area λ/4 layer 7. The circularlypolarized light passes through the liquid crystal layer 10′ and reachesthe reflective electrode 3 without changing the polarization statethereof, and is reflected by the reflective electrode 3. When thecircularly polarized light is reflected by the reflective electrode 3,the rotating direction thereof is reversed. The thus reflectedcircularly polarized light passes through the liquid crystal layer 10′again, is incident on the reflective-area λ/4 layer 7, where it islinearly polarized in a direction perpendicular to the transmission axisof the polarizer 9, and is absorbed by the polarizer 9.

In the transmissive area, light emitted from the backlight is incidentfrom the back and passes through the polarizer 5, where it is linearlypolarized in the direction parallel to the transmission axis of thepolarizer 5. The linearly polarized light passes through the liquidcrystal layer 10′ and reaches the polarizer 9 without changing thepolarization state thereof, and is absorbed by the polarizer 9.

In the liquid crystal display 1′ which is constructed as describedabove, similar to the liquid crystal display 1 according to the firstembodiment shown in FIG. 1, the reflective-area λ/4 layer 7, which isnecessary for the dark state display in the reflective area, is notprovided in the transmissive area. Accordingly, effects similar to thoseof the first embodiment can be obtained. In addition, since the liquidcrystal layer is in the 90° twisted nematic state in the transmissivearea, images can be displayed in a twisted nematic mode in thetransmissive area and the contrast can be increased.

In the above description, the liquid-crystal molecules in the liquidcrystal layer are oriented approximately perpendicular to the substrateswhen a voltage is applied, and the liquid-crystal layer has a phasedifference of λ/4 in the reflective area and is in the 90° twistednematic state in the transmissive area when no voltage is applied.According to the present invention, however, the construction of theliquid crystal display may also be opposite. More specifically, theliquid crystal layer may also have a phase difference of λ/4 in thereflective area and be in the 90° twisted nematic state in thetransmissive area when a voltage is applied.

According to the second embodiment, the retardation layer is not limitedto that having a single-layer structure consisting of thereflective-area λ/4 layer, and may also have a two-layer structureconsisting of a reflective-area λ/4 layer and an additional retardationlayer which compensates for the chromatic dispersion of thereflective-area λ/4 layer, as explained above with reference to FIG. 4in the first embodiment. A case in which a λ/2 layer is provided as theretardation layer which compensates for the chromatic dispersion of thereflective-area λ/4 layer will be described below with reference toFIGS. 10A to 10C. FIG. 10C shows a schematic sectional view of the mainpart of a liquid crystal display 21′, and FIGS. 10A and 10B show theoptical constructions in a reflective area and a transmissive area,respectively, of the liquid crystal display 21′. In FIGS. 10A to 10C,components similar to those of the liquid crystal display 21 shown inFIG. 4 and those of the liquid crystal display 1′ shown in FIGS. 7A to7C are denoted by the same reference numerals, and explanations thereofare thus omitted.

In the liquid crystal display 21′ according to this modification, aretardation layer having a two-layer structure consisting of areflective-area λ/2 layer 22 and a reflective-area λ/4 layer 7 isprovided in the reflective area, and no retardation layer is provided inthe transmissive area. In this case, in order for the combination of thereflective-area λ/2 layer 22 and the reflective-area λ/4 layer 7 toserve as a λ/4 layer over a wide wavelength range, the angle between theslow axis 22 a of the reflective-area λ/2 layer 22 and the slow axis 7 aof the reflective-area λ/4 layer 7 is set to 60°, the angle between theslow axis 22 a of the reflective-area λ/2 layer 22 and the transmissionaxis 9 a (or the absorption axis) of the polarizer 9 to 15°, and theangle between the slow axis 7 a of the reflective-area λ/2 layer 7 andthe transmission axis 9 a (or the absorption axis) of the polarizer 9 to75°.

The liquid-crystal orientations 10 t and 10 b in the reflective area areadjusted such that the phase difference of the liquid crystal layer 10′is λ/4 when light passes through the liquid crystal layer 10′ once whileno voltage is applied thereto, and are preferably parallel or nearlyperpendicular to the slow axis 7 a of the reflective-area λ/4 layer 7 sothat a residual retardation which occurs when a voltage is applied canbe adjusted by the reflective-area λ/4 layer 7.

As described above, in the liquid crystal display 21′, the retardationlayer having a two-layer structure is provided in the reflective area.Accordingly, in addition to the effects obtained by the above-describedliquid crystal display 1′ having the basic structure, images can bedisplayed in an electrically controlled birefringence (ECB) mode inwhich light leakage caused by the chromatic dispersion in the dark statedisplay is eliminated over a wide wavelength range in the reflectivearea, and the image quality can be improved.

In the second embodiment, not only the liquid crystal layer 10′ in thetransmissive area but also the liquid crystal layer 10′ in thereflective area may be in the twisted nematic state. The case in whichthe liquid crystal layer 10′ in the transmissive area is also in thetwisted nematic state will be described below with reference to FIGS.11A to 11C. In FIGS. 11A to 11C, components similar to those of theliquid crystal display 21′ shown in FIGS. 10A to 10C are denoted by thesame reference numerals, and explanations thereof are thus omitted.

A liquid crystal display 21 a according to this modification is similarto the liquid crystal display 21′ described above with reference toFIGS. 10A to 10C except for the liquid-crystal orientations in thereflective area.

More specifically, in the liquid crystal display 21 a shown in FIGS. 11Ato 11C, the liquid-crystal orientations 10 t and 10 b in the reflectivearea are set such that a liquid crystal layer 10′ is in atwisted-nematic state when no voltage is applied thereto. Accordingly,in the liquid crystal display 21 a, an angle between the alignmentdirections of alignment films (not shown) disposed between substrates 2and 6 so as to face the liquid crystal layer 10′ is set to apredetermined angle. This angle is determined in accordance with thecell gap and the birefringence of the liquid crystal layer 10′ such thatthe phase difference of the liquid crystal layer 10′ is λ/4 when lightpasses through the liquid crystal layer 10′ once while no voltage isapplied thereto.

When a voltage is applied to the liquid crystal layer 10′, theliquid-crystal molecules are aligned approximately perpendicular to thesubstrates 2 and 6, similar to the above-described cases.

When the liquid-crystal layer in the reflective area is in the twistednematic state as described above, the effective phase difference of theliquid crystal layer in the reflective area decreases. Therefore, thecell gap for obtaining a phase difference of λ/4 in the reflective areaincreases and the allowance for the cell gap increases accordingly. As aresult, the yield of the liquid crystal display can be increased.

Similar to the first embodiment, according to the second embodiment, theliquid crystal display may also be a full-color liquid crystal display.In addition, although the liquid crystal displays in which theretardation layer is provided on the substrate arranged on the displayside are explained in the above descriptions, the present invention isnot limited to this. The present invention is applicable as long as aretardation layer whose phase difference is different between thereflective area and the transmissive area is provided on at least one ofthe substrates. For example, the present invention may also be appliedto a case where the retardation layer is provided on the substrateadjacent to the backlight.

The constructions described above in the second embodiment may also beused in combination with each other, and effects specific to thecombined construction can be obtained in such a case.

Third Embodiment

Next, a transflective liquid crystal display according to a thirdembodiment of the present invention will be described below. The liquidcrystal display according to the third embodiment is characterized inthat the slow axis of a retardation layer is different between areflective area and a transmissive area. The basic construction of theliquid crystal display according to the third embodiment will bedescribed below with reference to FIG. 12. In FIG. 12, componentssimilar to those of the liquid crystal display 1 shown in FIG. 1 aredenoted by the same reference numerals, and explanations thereof arethus omitted.

In a liquid crystal display 51 shown in FIG. 12, a reflective electrode3 composed of a material with high reflectivity which defines areflective area and a transparent electrode 4 composed of a materialwith high transmittance which defines a transmissive area are providedon a main surface of a substrate 2. The reflective electrode 3 islaminated on the substrate 2 with an interlayer film 52 therebetween,and an alignment film 53 is laminated on the reflective electrode 3 andthe transparent electrode 4. In addition, a polarizer 5 is provided onthe other main surface of the substrate 2. Another substrate 6 whichreceives ambient light is placed on the display side, and areflective-area λ/4 layer 7 which serves as a retardation layer andcovers the reflective area and a transmissive-area λ/4 layer 55 whichalso serves as a retardation layer and covers the transmissive area areprovided on a main surface of the substrate 6 which faces the substrate2 with an alignment film 54 therebetween. In addition, a counterelectrode 8 which covers both the reflective area and the transmissivearea is provided on the reflective-area λ/4 layer 7 and thetransmissive-area λ/4 layer 55, and an alignment film 56 is provided onthe counter electrode 8. In addition, a polarizer 9 is provided on theother main surface of the substrate 6. A liquid crystal layer 10composed of a liquid crystal material is interposed between thesubstrate 2 and the substrate 6, and a backlight (not shown) fortransmissive display is disposed on the outer side the polarizer 5. Thetransmission axis of the polarizer 9 and that of the polarizer 5 areperpendicular to each other. In addition, the slow axis of thereflective-area λ/4 layer 7 which serves as the retardation layer in thereflective area is at an angle of 45° with respect to the transmissionaxis of the polarizer 9.

The slow axis of the transmissive-area λ/4 layer 55 which serves as theretardation layer in the transmissive area and that of thereflective-area λ/4 layer 7 which serves as the retardation layer in thereflective area extend in different directions. More specifically, theslow axis of the transmissive-area λ/4 layer 55 is parallel to thetransmission axis of the polarizer 9 provided on the substrate 6. Thereflective-area λ/4 layer 7 and the transmissive-area λ/4 layer 55 canbe obtained by, for example, applying a liquid-crystal polymer or anultraviolet-curable liquid crystal monomer in a nematic phase to thealignment film 54 on the substrate 6 which is subjected to multi-domainalignment in advance so that the alignment direction differs between thereflective area and the transmissive area. The multi-domain alignmentmay, of course, also be achieved by a photoalignment process, and thealignment film 54 can be omitted in such a case.

In the liquid crystal display 51 according to the third embodiment, aretardation layer which covers the entire area of the substrate 6 issubjected to multi-domain alignment so that the slow axis of thereflective-area λ/4 layer 7 and that of the transmissive-area λ/4 layer55 are different from each other. Thus, only the reflective-area λ/4layer 7 functions as a retardation layer. More specifically, the slowaxis of the transmissive-area λ/4 layer 55 is parallel to thetransmission axis of the polarizer 9 provided on the front, so that thetransmissive-area λ/4 layer 55 does not have an effective phasedifference. According to the above-described construction, transmissivedisplay can be achieved without providing an additional λ/4 layer on theback to compensate for the phase difference of the reflective-area λ/4layer 7.

The reflective-area λ/4 layer 7 and the transmissive-area λ/4 layer 55which serve as the retardation layers may also be disposed on the outerside of the substrate 6. However, they are preferably disposed on thesurface facing the liquid crystal layer 10, as shown in FIG. 12, so thatthe problem of parallax caused by the thickness of the substrate 6 canbe reduced.

The reflective-area λ/4 layer 7 and the transmissive-area λ/4 layer 55which serve as the retardation layers are obtained by, for example,applying a liquid-crystal polymer to the substrate 6 after an alignmentprocess, such as rubbing. More specifically, a photosensitiveliquid-crystal polymer is applied to the substrate 6 after the alignmentprocess, and an exposure process and a development process are performedso as to obtain the retardation layers having a desired pattern.Alternatively, the retardation layers may also be obtained by applyingan ultraviolet-curable liquid crystal monomer in a nematic phase to thesubstrate 6 or the alignment film and irradiating it with an ultravioletlight to grow a liquid-crystal polymer. In addition, the reflective-areaλ/4 layer 7 and the transmissive-area λ/4 layer 55 may also be obtainedby subjecting a film formed by applying a liquid-crystal polymer to aphotoalignment process. The phase differences of the retardation layerscan be arbitrarily adjusted by changing the thicknesses thereof. Theretardation layers may also be composed of, for example, oriented films.

In the present embodiment, the slow axis of the retardation layer in thetransmissive area may be parallel to any one of the transmission axisand the absorption axis of the polarizer on the display side and thetransmission axis and the absorption axis of the polarizer on the backas long as the retardation layer in the transmissive area does not havean effective phase difference.

The operation of displaying an image on the liquid crystal display 51shown in FIG. 12 will be described below with reference to FIGS. 13 and14. For convenience, the substrate 2, the counter electrode 8, and thealignment films are omitted in FIGS. 13 and 14. In addition, thethickness of the liquid crystal layer 10 is adjusted such that the phasedifference is λ/4 in the reflective area and λ/2 in the transmissivearea when light passes through the liquid crystal layer 10 once while novoltage is applied thereto. When no voltage is applied, theliquid-crystal orientation is approximately parallel to the substrates 2and 6 and is at an angle of 45° with respect to the transmission axis ofthe polarizer 9.

A case in which no voltage is applied to the liquid crystal layer 10 andthe light state is obtained will be described below with reference toFIG. 13.

In the reflective area, ambient light is incident from the display sideand passes through the polarizer 9, where it is linearly polarized in adirection parallel to the transmission axis of the polarizer 9. Thelinearly polarized light is converted into circularly polarized light asit passes through the reflective-area λ/4 layer 7, is converted intolinearly polarized light by the liquid crystal layer 10, and reaches thereflective electrode 3. The linearly polarized light is reflected by thereflective electrode 3 so that the traveling direction thereof isreversed, and is converted into circularly polarized light as it passesthrough the liquid crystal layer 10 again. The circularly polarizedlight passes through the reflective-area λ/4 layer 7 again, where it islinearly polarized in the direction parallel to the transmission axis ofthe polarizer 9, and passes through the polarizer 9.

In the transmissive area, light emitted from the backlight is incidentfrom the back and passes through the polarizer 5, where it is linearlypolarized in a direction parallel to the transmission axis of thepolarizer 5. The linearly polarized light passes through the liquidcrystal layer 10 having the phase difference of λ/2, where it islinearly polarized in a direction perpendicular to the transmission axisof the polarizer 5, that is, in the direction parallel to thetransmission axis of the polarizer 9, passes through thetransmissive-area λ/4 layer 55 without changing the polarization statethereof, and passes through the polarizer 9.

Next, a case in which a voltage is applied to the liquid crystal layer10 and the dark state is obtained will be described below with referenceto FIG. 14.

In the reflective area, ambient light is incident from the display sideand passes through the polarizer 9, where it is linearly polarized inthe direction parallel to the transmission axis of the polarizer 9. Thelinearly polarized light is converted into circularly polarized light asit passes through the reflective-area λ/4 layer 7. The circularlypolarized light passes through the liquid crystal layer 10 and reachesthe reflective electrode 3 without changing the polarization statethereof, and is reflected by the reflective electrode 3. When thecircularly polarized light is reflected by the reflective electrode 3,the rotating direction thereof is reversed. The thus reflectedcircularly polarized light passes through the liquid crystal layer 10again, is incident on the reflective-area λ/4 layer 7, where it islinearly polarized in a direction perpendicular to the transmission axisof the polarizer 9, and is absorbed by the polarizer 9.

In the transmissive area, light emitted from the backlight is incidentfrom the back and passes through the polarizer 5, where it is linearlypolarized in the direction parallel to the transmission axis of thepolarizer 5. The linearly polarized light passes through the liquidcrystal layer 10 and the transmissive-area λ/4 layer 55 and reaches thepolarizer 9 without changing the polarization state thereof, and isabsorbed by the polarizer 9.

As described above, in the liquid crystal display 51, the slow axis ofthe transmissive-area λ/4 layer 55 is parallel to the transmission axisof the polarizer 9, so that the transmissive-area λ/4 layer 55 does notfunction as a retardation layer. Accordingly, sufficient reflectivitycan be obtained in the reflective area due to the function of thereflective-area λ/4 layer 7 and transmissive display can be achieved inthe transmissive area without providing an additional retardation layeron the back to compensate for the phase difference of the retardationlayer on the display side. Accordingly, high quality, high contrastimages can be displayed in both reflective display and transmissivedisplay. In addition, it is not necessary to provide an additionalretardation layer on the back, so that the cell thickness can be reducedand costs can be reduced by the amount corresponding to the omittedretardation layer.

In the above description, liquid-crystal molecules in the liquid crystallayer are oriented approximately perpendicular to the substrates when avoltage is applied, and the liquid crystal layer has a phase differenceof λ/4 in the reflective area and λ/2 in the transmissive area when novoltage is applied. According to the present invention, however, theconstruction of the liquid crystal display may also be opposite. Morespecifically, the liquid crystal layer may also have a phase differenceof λ/4 in the reflective area and λ/2 in the transmissive area when avoltage is applied.

According to the present embodiment, the retardation layers are notlimited to those having a single-layer construction consisting of thereflective-area λ/4 layer 7 and the transmissive-area λ/4 layer 55, andmay also have a two-layer structure, as shown in FIG. 15. In FIG. 15,components similar to those of the liquid crystal display 51 shown inFIG. 12 are denoted by the same reference numerals, and explanationsthereof are thus omitted.

In a liquid crystal display 61 according to this modification, areflective-area λ/4 layer 7 and a transmissive-area λ/4 layer 55 whichserve as retardation layers, a reflective-area λ/2 layer 22 whichcompensates for the chromatic dispersion of the reflective-area λ/4layer 7, and a transmissive-area λ/2 layer 62 are provided on asubstrate 6 on the side facing a liquid crystal layer 10. The slow axisof the retardation layer in the transmissive area is different from thatof the retardation layer in the reflective area. More specifically, thetransmissive-area λ/2 layer 62 and the reflective-area λ/4 layer 7function as a λ/2 layer and a λ/4 layer, respectively, whereas thetransmissive-area λ/2 layer 62 and the transmissive-area λ/4 layer 55 donot function as retardation layers since the slow axes thereof areparallel to, for example, the transmission axis of a polarizer 9. Theretardation layers having the two-layer structure are obtained by, forexample, the following processes. That is, first, the reflective-areaλ/2 layer 22 and the transmissive-area λ/2 layer 62 are formed byapplying a liquid-crystal polymer or an ultraviolet-curable liquidcrystal monomer in a nematic phase to an alignment film 54 on thesubstrate 6 which is subjected to multi-domain alignment in advance sothat the alignment direction differs between the reflective area and thetransmissive area. Then, an alignment film 63, which is subjected tomulti-domain alignment so that the alignment direction differs betweenthe reflective area and the transmissive area, is provided on the λ/2layers. Then, the reflective-area λ/4 layer 7 and the transmissive-areaλ/4 layer 55 are formed by applying a liquid-crystal polymer or anultraviolet-curable liquid crystal monomer in a nematic phase toalignment film 63. The multi-domain alignment may, of course, also beachieved by a photoalignment process.

As described above, the retardation layers have a two-layer structure,and the slow axis of the retardation layer in the reflective area isdifferent from that of the retardation layer in the transmissive area.Thus, according to the liquid crystal display 61, in addition to theeffects obtained by the liquid crystal display 51 having the basicstructure of the present embodiment, light leakage caused by thechromatic dispersion in the dark state display can be eliminated over awide wavelength range and the image quality can be improved.

The present invention is not limited to liquid crystal displays in whichthe retardation layers are provided on the substrate 6 arranged on thedisplay side, and may also be applied to liquid crystal displays inwhich the retardation layers are provided on the substrate 2 adjacent tothe backlight. For example, in a liquid crystal display 71 shown in FIG.16, a reflective electrode 3 and a transparent electrode 4 are providedon a substrate 2 arranged on the back, and a reflective-area λ/4 layer 7and a transmissive-area λ/4 layer 55 which serve as retardation layersare laminated on the reflective electrode 3 and the transparentelectrode 4, respectively, with an alignment film 54 therebetween. Thereflective-area λ/4 layer 7 and the transmissive-area λ/4 layer 55 areconstructed similarly to those described with reference to FIG. 12.

In this case, a transparent electrode (not shown) for reliably drivingthe liquid crystal may be disposed between the reflective-area λ/4 layer7 and an alignment film 53 for driving the liquid crystal and betweenthe transmissive-area λ/4 layer 55 and the alignment film 53. When thistransparent electrode is provided, a plug is provided for connecting thetransparent electrode to thin-film transistors (TFTs). In addition, inthis case, it is not necessary to provide the transparent electrode 4between the substrate 2 and the transmissive-area λ/4 layer 55.

Although the reflective-area λ/4 layer 7 functions as a retardationlayer, the transmissive-area λ/4 layer 55 does not function as aretardation layer since the slow axis thereof is parallel to, forexample, the transmission axis of the polarizer 9. When the retardationlayers are provided on the substrate adjacent to the backlight, as inthe liquid crystal display 71 shown in FIG. 16, sufficient reflectivitycan be obtained in the reflective area due to the function of thereflective-area λ/4 layer 7 and transmissive display can be achieved inthe transmissive area without providing an additional retardation layeron the display side to compensate for the phase difference of theretardation layer on the back. Accordingly, similar to theabove-described liquid crystal displays, high quality, high contrastimages can be displayed in both reflective display and transmissivedisplay. In addition, it is not necessary to provide an additionalretardation layer on the display side, so that the cell thickness can bereduced and costs can be reduced by the amount corresponding to theomitted retardation layer.

In addition, according to the present embodiment, the liquid crystaldisplay may also be a full-color liquid crystal display, as shown inFIG. 17.

In a liquid crystal display 81 shown in FIG. 17, color filters 42R, 42G,and 42B corresponding to red, green, and blue dots, respectively, areprovided on a substrate 6 on the side facing a liquid crystal layer 10.In addition, a reflective-area λ/4 layer 7R and a transmissive-area λ/4layer 55R, a reflective-area λ/4 layer 7G and a transmissive-area λ/4layer 55CA and a reflective-area λ/4 layer 7B and a transmissive-areaλ/4 layer 55B, which serve as reflective-area retardation layers, areprovided on the color filters 42R, 42Q and 42B, respectively. Inaddition, a counter electrode 8 is provided on these retardation layerswith an overcoat layer 43 therebetween.

The slow axis is different between the reflective area and thetransmissive area in each pair of the reflective-area λ/4 layer 7R andthe transmissive-area λ/4 layer 55R, the reflective-area λ/4 layer 7Gand the transmissive-area λ/4 layer 55CA and the reflective-area λ/4layer 7B and the transmissive-area λ/4 layer 55B, so that theretardation layers in the transmissive area do not function. Therefore,similar to the above-described liquid crystal displays, it is notnecessary to provide additional retardation layers on the back tocompensate for the phase difference of the retardation layers used forreflective display and the number of retardation layers can be reduced.

In the liquid crystal display 81 according to this modification, thethicknesses of the reflective-area λ/4 layer 7R and thetransmissive-area λ/4 layer 55R, the reflective-area λ/4 layer 7G andthe transmissive-area λ/4 layer 55G, and the reflective-area λ/4 layer7B and the transmissive-area λ/4 layer 55B, which serve asreflective-area retardation layers, are adjusted in accordance with thetransmission wavelengths of the color filters 42R, 42Q and 42B,respectively, so that each retardation layer has a phase difference ofλ/4. Accordingly, the influence of the chromatic dispersion of eachcolor can be reduced and the image quality can be improved.

The present invention is not limited to the case where the slow axis ofthe retardation layer in the transmissive area is completely parallel orperpendicular to the transmission axis of the polarizer arranged on thefront or back so that the retardation layer in the transmission areadoes not function at all, and the slow axis of the retardation layer inthe transmissive area may also be slightly shifted. For example, theslow axis of the retardation layer in the transmissive area may alsohave a phase difference which is determined by taking variouscharacteristics of the liquid crystal layer into account. In such acase, preferably, the displacement of the slow axis of the retardationlayer in the transmissive area is set such that the phase difference inthe transmissive area cancels a residual phase difference in the liquidcrystal layer which occurs when sufficient voltage is applied to theliquid crystal layer. Accordingly, compared to the case in which theretardation layer in the transmissive area does not function at all, thedarkness in the dark state display can be increased in the transmissivearea and the image quality can be improved.

According to the third embodiment, the slow axis of the retardationlayer in the transmissive area is parallel to the transmission axis ofthe polarizer on the front. However, the effects of the presentinvention may also be obtained when the slow axis of the retardationlayer in the transmissive area is parallel to the transmission axis ofthe polarizer on the back.

Fourth Embodiment

Next, a transflective liquid crystal display according to a fourthembodiment of the present invention will be described below. The liquidcrystal display according to the fourth embodiment is obtained bycombining the constructions according to the above-described second andthird embodiments. The basic construction according to the fourthembodiment will be described below with reference to FIGS. 18A to 18C.FIG. 18C shows a schematic sectional view of the main part of a liquidcrystal display 51′, and FIGS. 18A and 18B show the opticalconstructions in a reflective area and a transmissive area,respectively, of the liquid crystal display 51′. In FIGS. 18A to 18C,components similar to those of the liquid crystal display 51 shown inFIG. 12 which is described above in the third embodiment and those ofthe liquid crystal display 1′ shown FIGS. 7A to 7C which is describedabove in the second embodiment are denoted by the same referencenumerals, and explanations thereof are thus omitted.

The liquid crystal display 51′ shown in FIGS. 18A to 18C is differentfrom the liquid crystal display shown in FIG. 12 which is describedabove in the third embodiment in that the orientations of the liquidcrystal layer (liquid-crystal orientations) in the reflective area andthe transmissive area are adjusted similarly to the second embodiment,and other constructions are similar to those of the third embodiment.

With reference to FIGS. 18A to 18C, in the liquid crystal display 51′,the liquid-crystal orientations 10 t and 10 b in the reflective area isset such that it is parallel to substrates 2 and 6 and are at an angleof 45° with respect to the transmission axes of polarizers 5 and 9 whenno voltage is applied to a liquid crystal layer 10′. In addition, theliquid crystal layer 10′ is adjusted such that the phase difference isλ/4 in the reflective area when light passes through the liquid crystallayer 10′ once while no voltage is applied thereto.

In the transmissive area, the liquid-crystal orientation 10 t on theside facing the substrate 6 is parallel to the transmission axis 9 a ofthe polarizer 9 and the liquid-crystal orientation 10 b on the sidefacing the substrate 2 is parallel to the transmission axis 5 a of thepolarizer 5, so that 90° twisted nematic state where the liquid-crystalmolecules are twisted by 90° is obtained, when no voltage is applied tothe liquid crystal layer 10′.

When a voltage is applied to the liquid crystal layer 10′, theliquid-crystal molecules are aligned approximately perpendicular to thesubstrates 2 and 6 in both the reflective area and the transmissivearea.

In addition, in the liquid crystal display 51′, similar to theconstruction according to the third embodiment which is described abovewith reference to FIG. 12, an interlayer film 52 is provided in thereflective area and a transmissive-area λ/4 layer 55 is provided on thesubstrate 6 in the transmissive area.

The thickness of the interlayer film 52 provided in the reflective areais set to adjust the cell gap, that is, the thickness of the liquidcrystal layer 10′, in the transmissive area and the reflective area.More specifically, the cell gap is set such that the liquid crystallayer 10′ has a phase difference of λ/4 in the reflective area andliquid-crystal molecules in the transmissive area are in a 90° twistednematic state and satisfy the Mauguin condition so that optical activityis maintained when no voltage is applied to the liquid crystal layer10′. Therefore, the interlayer film 52 may also be omitted from theliquid crystal display 51′ if the above-described conditions can besatisfied without the interlayer film 52.

Similar to the third embodiment, the slow axis of the transmissive-areaλ/4 layer 55 provided on the substrate 6 in the transmissive area isparallel to the transmission axis of the polarizer 9 arranged on thefront, so that an effective phase difference does not occur. Accordingto the above-described construction, transmissive display can beachieved without providing an additional retardation layer on the backto compensate for the phase difference of the reflective-area λ/4 layer7. The slow axis of the transmissive-area λ/4 layer 55 in thetransmissive area may be parallel to any one of the transmission axisand the absorption axis of the polarizer on the display side and thetransmission axis and the absorption axis of the polarizer on the backas long as the retardation layer in the transmissive area does not havean effective phase difference.

The operation of displaying an image on the liquid crystal display 51′shown in FIGS. 18A to 18C will be described below with reference toFIGS. 19 and 20. For convenience, the substrate 2, a counter electrode8, and the alignment films are omitted in FIGS. 19 and 20.

A case in which no voltage is applied to the liquid crystal layer 10′and the light state is obtained will be described below with referenceto FIG. 19.

In the reflective area, ambient light is incident from the display sideand passes through the polarizer 9, where it is linearly polarized in adirection parallel to the transmission axis of the polarizer 9. Thelinearly polarized light is converted into circularly polarized light asit passes through the reflective-area λ/4 layer 7, is converted intolinearly polarized light by the liquid crystal layer 10′, and reaches areflective electrode 3. The linearly polarized light is reflected by thereflective electrode 3 so that the traveling direction thereof isreversed, and is converted into circularly polarized light as it passesthrough the liquid crystal layer 10′ again. The circularly polarizedlight passes through the reflective-area λ/4 layer 7 again, where it islinearly polarized in the direction parallel to the transmission axis ofthe polarizer 9, and passes through the polarizer 9.

In the transmissive area, light emitted from a backlight is incidentfrom the back and passes through the polarizer 5, where it is linearlypolarized in a direction parallel to the transmission axis of thepolarizer 5. The linearly polarized light passes through the liquidcrystal layer 10′ in the 90° twisted nematic state, where it is linearlypolarized in a direction perpendicular to the transmission axis of thepolarizer 5, that is, in the direction parallel to the transmission axisof the polarizer 9. The linearly polarized light passes through thetransmissive-area λ/4 layer 55 without changing the polarization statethereof, and passes through the polarizer 9.

Next, a case in which a voltage is applied to the liquid crystal layer10′ and the dark state is obtained will be described below withreference to FIG. 20.

In the reflective area, ambient light is incident from the display sideand passes through the polarizer 9, where it is linearly polarized inthe direction parallel to the transmission axis of the polarizer 9. Thelinearly polarized light is converted into circularly polarized light asit passes through the reflective-area λ/4 layer 7. The circularlypolarized light passes through the liquid crystal layer 10′ and reachesthe reflective electrode 3 without changing the polarization statethereof, and is reflected by the reflective electrode 3. When thecircularly polarized light is reflected by the reflective electrode 3,the rotating direction thereof is reversed. The thus reflectedcircularly polarized light passes through the liquid crystal layer 10′again, is incident on the reflective-area λ/4 layer 7, where it islinearly polarized in a direction perpendicular to the transmission axisof the polarizer 9, and is absorbed by the polarizer 9.

In the transmissive area, light emitted from the backlight is incidentfrom the back and passes through the polarizer 5, where it is linearlypolarized in the direction parallel to the transmission axis of thepolarizer 5. The linearly polarized light passes through the liquidcrystal layer 10′ and the transmissive-area λ/4 layer 55 and reaches thepolarizer 9 without changing the polarization state thereof, and isabsorbed by the polarizer 9.

In the liquid crystal display 51′ which is constructed as describedabove, similar to the liquid crystal display 51 shown in FIG. 12, thereflective-area λ/4 layer 7, which is necessary for the dark statedisplay in the reflective area, is provided only in the reflective area,and the transmissive-area λ/4 layer 55 whose slow axis is parallel tothe transmission axis of the polarizer 9 is provided in the transmissivearea. Accordingly, effects similar to those of the third embodiment canbe obtained. In addition, since the liquid crystal layer is in the 90°twisted nematic state in the transmissive area, images can be displayedin a twisted nematic mode in the transmissive area and the contrast canbe increased.

In the above description, the liquid-crystal molecules in the liquidcrystal layer are oriented approximately perpendicular to the substrateswhen a voltage is applied, and the liquid-crystal layer has a phasedifference of λ/4 in the reflective area and is in the 90° twistednematic state in the transmissive area when no voltage is applied.According to the present invention, however, the construction of theliquid crystal display may also be opposite. More specifically, theliquid crystal layer may also have a phase difference of λ/4 in thereflective area and be in the 90° twisted nematic state in thetransmissive area when a voltage is applied.

According to the present embodiment, the retardation layers are notlimited to those having a single-layer structure consisting of thereflective-area λ/4 layer 7 and the transmissive-area λ/4 layer 55, andmay also have a two-layer structure, as shown in FIGS. 21A to 21C. InFIGS. 21A to 21C, components similar to those of the liquid crystaldisplay 51′ shown in FIGS. 18A to 18C are denoted by the same referencenumerals, and explanations thereof are thus omitted.

In a liquid crystal display 61′ according to this modification, areflective-area λ/4 layer 7 and a transmissive-area λ/4 layer 55 whichserve as retardation layers, a reflective-area λ/2 layer 22 whichcompensates for the chromatic dispersion of the reflective-area λ/4layer 7, and a transmissive-area λ/2 layer 62 are provided on asubstrate 6 on the side facing a liquid crystal layer 10′. The slow axesof the retardation layers in the transmissive area are different fromthose of the retardation layers in the reflective area. Morespecifically, in order for the combination of the reflective-area λ/4layer 7 and the reflective-area λ/2 layer 22 to serve as a λ/4 layerover a wide wavelength range, the angle between the slow axes 7 a and 22a thereof is set to 60° and the slow axes 7 a and 22 a are at an angleof 15° with respect to the transmission axes 5 a and 9 a of thepolarizers 5 and 9, respectively. In addition, the transmissive-area λ/4layer 55 and the transmissive-area λ/2 layer 62 do not function asretardation layers since the slow axes 55 a and 62 a thereof areparallel to, for example, the transmission axis 9 a of the polarizer 9.

The retardation layers having a two-layer structure can be obtained byprocesses similar to those described above in the third embodiment.

In this case, the liquid-crystal orientations 10 t and 10 b in thereflective area are set such that they are parallel to the substrates 2and 6 and are at an angle of 0° or 90° with respect to the slow axis 7 aof the reflective-area λ/4 layer 7 when no voltage is applied to theliquid crystal layer 10′. This setting is for adjusting the residualretardation, and the liquid-crystal orientations 10 t and 10 b may be inany direction if the residual retardation is negligibly small. Inaddition, the liquid crystal layer 10′ in the reflective area isadjusted such that the phase difference is λ/4 when light passes throughthe liquid crystal layer 10′ once while no voltage is applied thereto.The liquid-crystal orientations 10 t and 10 b in the transmissive areaare the same as those in the liquid crystal display 51′ shown in FIGS.18A to 18C.

As described above, in the liquid crystal display 61′, the retardationlayers have a two-layer structure and the slow axis of the retardationlayer in the reflective area is different from that of the retardationlayer in the transmissive area. Accordingly, in addition to the effectsobtained by the liquid crystal display 51′ having the basic structure,light leakage caused by the chromatic dispersion in the dark statedisplay can be eliminated, particularly in the reflective area, over awide wavelength range and the image quality can be improved.

The present invention is not limited to liquid crystal displays in whichthe retardation layers are provided on the substrate 6 arranged on thedisplay side, and may also be applied to liquid crystal displays inwhich the retardation layers are provided on the substrate 2 adjacent tothe backlight, as in the liquid crystal display 71 which is describedabove with reference to FIG. 16 in the third embodiment. For example, ina liquid crystal display 71′ shown in FIG. 22, a reflective electrode 3and a transparent electrode 4 are provided on a substrate 2 arranged onthe back, and a reflective-area λ/4 layer 7 and a transmissive-area λ/4layer 55 which serve as retardation layers are laminated on thereflective electrode 3 and the transparent electrode 4, respectively,with an alignment film 54 therebetween. The reflective-area λ/4 layer 7and the transmissive-area λ/4 layer 55 are constructed similarly tothose described with reference to FIG. 12.

Similar to the case described above with reference to FIG. 16, atransparent electrode (not shown) for reliably driving the liquidcrystal may be disposed between the reflective-area λ/4 layer 7 and analignment film 53 for driving the liquid crystal and between thetransmissive-area λ/4 layer 55 and the alignment film 53.

Although the reflective-area λ/4 layer 7 functions as a retardationlayer, the transmissive-area λ/4 layer 55 does not function as aretardation layer since the slow axis thereof is parallel to, forexample, the transmission axis of the polarizer 9. When the retardationlayers are provided on the substrate adjacent to the backlight, as inthe liquid crystal display 71′ shown in FIG. 22, sufficient reflectivitycan be obtained in the reflective area due to the function of thereflective-area λ/4 layer 7 and transmissive display can be achieved inthe transmissive area without providing an additional retardation layeron the display side to compensate for the phase difference of theretardation layer on the back. Accordingly, similar to theabove-described liquid crystal displays, high quality, high contrastimages can be displayed in both reflective display and transmissivedisplay. In addition, it is not necessary to provide an additionalretardation layer on the display side, so that the cell thickness can bereduced and costs can be reduced by the amount corresponding to theomitted retardation layer.

In addition, according to the present embodiment, the liquid crystaldisplay may also be a full-color liquid crystal display, as in theliquid crystal display shown in FIG. 17 which is described above in thethird embodiment.

In a liquid crystal display 81′ shown in FIG. 23, color filters 42R,42G, and 42B corresponding to red, green, and blue dots, respectively,are provided on a substrate 6 on the side facing a liquid crystal layer10′. In addition, a reflective-area λ/4 layer 7R and a transmissive-areaλ/4 layer 55R, a reflective-area λ/4 layer 7G and a transmissive-areaλ/4 layer 55G, and a reflective-area λ/4 layer 7B and atransmissive-area λ/4 layer 55B, which serve as reflective-arearetardation layers, are provided on the color filters 42R, 42Q, and 42B,respectively. In addition, a counter electrode 8 is provided on theseretardation layers with an overcoat layer 43 therebetween.

The slow axis is different between the reflective area and thetransmissive area in each pair of the reflective-area λ/4 layer 7R andthe transmissive-area λ/4 layer 55R, the reflective-area λ/4 layer 7Gand the transmissive-area λ/4 layer 55G, and the reflective-area λ/4layer 7B and the transmissive-area λ/4 layer 55B, so that theretardation layers in the transmissive area do not function. Therefore,similar to the above-described liquid crystal displays, it is notnecessary to provide additional retardation layers on the back tocompensate for the phase difference of the retardation layers used forreflective display and the number of retardation layers can be reduced.

In the liquid crystal display 81′ according to this modification, thethicknesses of the reflective-area λ/4 layer 7R and thetransmissive-area λ/4 layer 55R, the reflective-area λ/4 layer 7G andthe transmissive-area λ/4 layer 55G, and the reflective-area λ/4 layer7B and the transmissive-area λ/4 layer 55B, which serve asreflective-area retardation layers, are adjusted in accordance with thetransmission wavelengths of the color filters 42R, 42G, and 42B,respectively, so that each retardation layer has a phase difference ofλ/4. Accordingly, the influence of chromatic dispersion of each colorcan be reduced and the image quality can be improved.

In the fourth embodiment, not only the liquid crystal layer 10′ in thetransmissive area but also the liquid crystal layer 10′ in thereflective area may be in the twisted nematic state. The case in whichthe liquid crystal layer 10′ in the transmissive area is also in thetwisted nematic state will be described below with reference to FIGS.24A to 24C. In FIGS. 24A to 24C, components similar to those of theliquid crystal display 61′ shown in FIGS. 21A to 21C are denoted by thesame reference numerals, and explanations thereof are thus omitted.

A liquid crystal display 61 a according to this modification is similarto the liquid crystal display 61′ described above with reference toFIGS. 21A to 21C except for the liquid-crystal orientations in thereflective area.

More specifically, in the liquid crystal display 61 a shown in FIGS. 24Ato 24C, the liquid-crystal orientations 10 t and 10 b in the reflectivearea is set such that a liquid crystal layer 10′ is in a twisted-nematicstate when no voltage is applied thereto. Accordingly, in the liquidcrystal display 61 a, an angle between the alignment directions ofalignment films (not shown) disposed between substrates 2 and 6 so as toface the liquid crystal layer 10′ is set to a predetermined angle. Thisangle is determined in accordance with the cell gap and thebirefringence of the liquid crystal layer 10′ such that the phasedifference of the liquid crystal layer 10′ is λ/4 when light passesthrough the liquid crystal layer 10′ once while no voltage is appliedthereto.

Accordingly, as shown in FIGS. 25A to 25C, the liquid-crystalorientation 10 b on the side facing the substrate 2 may be at an angleof 90° with respect to the liquid-crystal orientation 10 t on the sidefacing the substrate 6. In such a case, the alignment films which facethe liquid crystal layer 10′ may have the same alignment direction inthe reflective area and the transmissive area, so that the process ofmulti-domain alignment can be omitted.

In the liquid crystal display 61 a shown in FIGS. 24A to 24C and FIGS.25A to 25C, when a voltage is applied to the liquid crystal layer 10′,the liquid-crystal molecules are aligned approximately perpendicular tothe substrates 2 and 6, similar to the above-described cases.

When the liquid-crystal layer in the reflective area is in the twistednematic state as described above, effective phase difference of theliquid crystal layer in the reflective area decreases. Therefore, thecell gap for obtaining a phase difference of λ/4 in the reflective areaincreases and the allowance for the cell gap increases accordingly. As aresult, the yield of the liquid crystal display can be increased.

The fourth embodiment of the present invention is not limited to thecase where the slow axis of the retardation layer in the transmissivearea is completely parallel or perpendicular to the transmission axis ofthe polarizer arranged on the front or back so that the retardationlayer in the transmission area does not function at all, and the slowaxis of the retardation layer in the transmissive area may also beslightly shifted. For example, the slow axis of the retardation layer inthe transmissive area may also have a phase difference which isdetermined by taking various characteristics of the liquid crystal layerinto account. In such a case, preferably, the displacement of the slowaxis of the retardation layer in the transmissive area is set such thatthe phase difference in the transmissive area cancels a residual phasedifference in the liquid crystal layer which occurs when sufficientvoltage is applied to the liquid crystal layer. Accordingly, compared tothe case in which the retardation layer in the transmissive area doesnot function at all, the darkness in the dark state display can beincreased in the transmissive area and the image quality can beimproved.

According to the fourth embodiment, the slow axis of the retardationlayer in the transmissive area is parallel to the transmission axis ofthe polarizer on the front. However, the effects of the presentinvention may also be obtained when the slow axis of the retardationlayer in the transmissive area is parallel to the transmission axis ofthe polarizer on the back.

The constructions described above in the fourth embodiment may also beused in combination with each other, and effects specific to thecombined construction can be obtained in such a case.

EXAMPLES

Examples in which the present invention is applied will be describedbelow in conjunction with experiment results. Examples 1 to 5 correspondto the first embodiment, Examples 6 to 8 correspond to the secondembodiment, Examples 9 to 13 correspond to the third embodiment, andExamples 14 to 19 correspond to the fourth embodiment.

Example 1

In Example 1, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 1 shownin FIG. 1 was manufactured.

First, a substrate to be arranged on the back having thin filmtransistors (TFTs) for active-matrix driving of a liquid crystal layerwas manufactured. A method for forming the TFTs will be described belowwith reference to FIG. 26.

A borosilicate glass (Corning 7059 produced by Corning Incorporated) wasused as a substrate 2. First, a gate electrode 91 composed of Mo, MoW,etc., a gate insulator 92, and amorphous silicon were successivelydeposited on the substrate 2 and patterned, and the amorphous siliconwas crystallized by annealing it with an excimer laser so as to form asemiconductor thin film 93. Then, P and B were doped into thesemiconductor thin film 93 on both sides of the gate electrode 91, sothat n-channel and p-channel TFTs were obtained. Then, a firstinterlayer insulator 94 composed of SiO₂ was formed on the substrate 2so as to cover the TFTs.

Then, holes were formed in the first interlayer insulator 94 by, forexample, etching, at positions corresponding to a source and a drain ofthe semiconductor thin film 93, and signal lines 95 composed of Al wereformed in a predetermined shape by patterning.

Next, a second interlayer insulator 96 having both a function as ascattering layer for causing scattered reflection and a function as aninterlayer insulator was formed on the substrate 2 so as to cover theTFTs and the signal lines 95. Then, a transparent electrode 4 composedof indium tin oxide (ITO) was formed on the second interlayer insulator96 at regions corresponding to the transmissive area and a reflectiveelectrode 3 composed of Ag was formed on the second interlayer insulator96 at regions corresponding to the reflective area. Accordingly, thesubstrate to be arranged on the side adjacent to the backlight wasmanufactured as shown in FIG. 26.

Then, a black matrix composed of Cr was formed on a counter substrate,and red, green, and blue (RGB) filters were formed on the countersubstrate in a predetermined pattern. Then, an alignment film was formedon the color filters by applying polyimide to the color filters byprinting and rubbing it.

Then, an ultraviolet-curable liquid crystal monomer (RMM 34 produced byMerck Ltd.) was spin-coated on the alignment film and was subjected toan exposure process and a development process, so that a reflective-areaλ/4 layer which served as a retardation layer was formed only in thereflective area and no retardation layer was formed in the transmissivearea. Since this ultraviolet-curable liquid crystal monomer cannot besufficiently polymerized when oxygen exists, the above-describedprocesses were performed in N₂ atmosphere. In addition, since thebirefringence Δn of RMM 34 is 0.145, the thickness of the retardationlayer formed by spin coating was set to 950 nm. Accordingly, theretardation was within the range of 135 nm to 140 nm. After theretardation layer was formed, a counter electrode was formed bysputtering ITO.

Then, normal cell processes were performed. More specifically, analignment film was formed on the counter electrode by applying polyimideto the counter electrode by printing and rubbing it.

The rubbing direction of the alignment film adjacent to the retardationlayer was the same as the orientation of the liquid-crystal polymer onthe side facing the retardation layer. In addition, the rubbingdirection of the alignment film on the substrate having the TFTs was setantiparallel to the rubbing direction of the alignment film adjacent tothe retardation layer.

The substrate having the TFTs and the counter substrate having theretardation layer were assembled together by normal processes, and aliquid crystal panel whose optical construction was the same as that ofthe liquid crystal display shown in FIG. 1 and which was provided withthe color filters was thus obtained. Then, it was experimentallyconfirmed that high-contrast images could be displayed by using thispanel.

Example 2

In Example 2, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 21 shownin FIG. 4 was manufactured.

First, a substrate having TFTs similar to that shown in FIG. 26 wasformed by processes similar to those of Example 1.

Then, color filters were formed on a counter substrate by processessimilar to those of Example 1, and an alignment film was formed on thecolor filters by applying polyimide to the color filters by printing andrubbing it.

Then, an ultraviolet-curable liquid crystal monomer was applied to thealignment film such that the λ/2 condition was satisfied, and waspatterned such that a retardation layer was formed only in thereflective area. Accordingly, a reflective-area λ/2 layer which servedas a retardation layer was formed.

Next, polyimide was applied by printing and was rubbed in a direction atan angle of 60° with respect to the rubbing direction of theabove-described alignment film. Then, an ultraviolet-curable liquidcrystal monomer was applied such that the λ/4 condition was satisfied,and was patterned such that a retardation layer was formed only in thereflective area. Accordingly, a reflective-area λ/4 layer which servedas a retardation layer was formed. After the retardation layer having atwo-layer structure consisting of the reflective-area λ/2 layer and thereflective-area λ/4 layer was formed, a counter electrode was formed bysputtering ITO.

Then, normal cell processes were performed. More specifically, analignment film was formed on the counter electrode by applying polyimideto the counter electrode by printing and rubbing it. The rubbing processwas performed such that the orientation of the liquid-crystal layer isbetween λ/2 and λ/4.

The substrate having the TFTs and the counter substrate having theretardation layer were assembled together by normal processes, and aliquid crystal panel whose optical construction was the same as that ofthe liquid crystal display shown in FIG. 4 and which was provided withthe color filters was thus obtained. Then, it was experimentallyconfirmed that high-contrast images could be displayed by using thispanel.

Example 3

In Example 3, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 31 shownin FIG. 5 was manufactured.

First, a substrate having TFTs similar to that shown in FIG. 26 wasformed by processes similar to those of Example 1.

Then, color filters were formed on a counter substrate by processessimilar to those of Example 1, and an alignment film was formed on thecolor filters by applying polyimide to the color filters by printing andrubbing it.

Next, a retardation layer consisting of a reflective-area λ/2 layer anda reflective-area λ/4 layer was formed only in the reflective area byprocesses similar to those of Example 2.

Next, polyimide was applied by printing and was rubbed in a direction atan angle of 90° with respect to the center line between the slow axes ofthe reflective-area λ/2 layer and the reflective-area λ/4 layer. Then, atransmissive-area retardation layer for canceling a residual phasedifference which occurred when a voltage was applied to the liquidcrystal layer was formed only in the transmissive area. Thetransmissive-area retardation layer had a phase difference of 30 nm,which was the same as the residual phase difference which occurred whena voltage was applied to the liquid crystal layer.

After the retardation layer in the reflective area and thetransmissive-area retardation layer were formed, a counter electrode wasformed by sputtering ITO.

Then, normal cell processes were performed. More specifically, analignment film was formed on the counter electrode by applying polyimideto the counter electrode by printing and rubbing it.

The substrate having the TFTs and the counter substrate having theretardation layer were assembled together by normal processes, and aliquid crystal panel whose optical construction was the same as that ofthe liquid crystal display shown in FIG. 5 and which was provided withthe color filters was thus obtained. Then, it was experimentallyconfirmed that the dark state display in transmissive display could beimproved compared to the liquid crystal panel of Example 1 andhigh-contrast images could be displayed by using this panel.

Example 4

In Example 4, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 41 shownin FIG. 6 was manufactured.

First, a substrate having TFTs similar to that shown in FIG. 26 wasformed by processes similar to those of Example 1.

Then, color filters were formed on a counter substrate by processessimilar to those of Example 1, and an alignment film was formed on thecolor filters by applying polyimide to the color filters by printing andrubbing it.

Then, an ultraviolet-curable liquid crystal monomer was spin-coated onthe alignment film and was subjected to an exposure process and adevelopment process, so that reflective-area λ/4 layers which served asretardation layers were formed only in the reflective area and noretardation layer was formed in the transmissive area.

The thickness of each retardation layer was set in accordance with aphase difference of its corresponding pixel. More specifically, thethickness of the retardation layer for a green pixel was set to 950 nmas in Example 1. In addition, the thickness of the retardation layer fora blue pixel was set to 730 nm since the birefringence Δn was about0.155 according to the retardation at the blue pixel, and the thicknessof the retardation layer for a red pixel was set to 1200 nm since thebirefringence Δn was about 0.135 according to the retardation at the redpixel.

After the retardation layers were formed, a counter electrode was formedby sputtering ITO.

Then, normal cell processes were performed. More specifically, analignment film was formed on the counter electrode by applying polyimideto the counter electrode by printing and rubbing it.

The substrate having the TFTs and the counter substrate having theretardation layers were assembled together by normal processes, and aliquid crystal panel whose optical construction was the same as that ofthe liquid crystal display shown in FIG. 6 and which was provided withthe color filters was thus obtained. Then, it was experimentallyconfirmed that the dark state display could be improved compared to theliquid crystal panel of Example 1 and high-contrast images could bedisplayed by using this panel.

Example 5

In Example 5, a liquid crystal panel was manufactured in which aretardation layer was formed on a substrate having TFTs arrangedadjacent to a backlight in a reflective area thereof.

First, a substrate having TFTs similar to that shown in FIGS. 26 wasformed by processes similar to those of Example 1. Then, areflective-area λ/4 layer which served as a retardation layer was formedon a reflective electrode provided on this substrate, and an ITOelectrode was formed on the reflective-area λ/4 layer by sputtering.

In addition, a counter electrode was formed on a counter substrate bysputtering ITO, and no retardation layer was formed on this substrate.Then, an alignment film was formed on the counter electrode by applyingpolyimide to the counter electrode by printing and rubbing it.

The substrate having the TFTs and the retardation layer and the countersubstrate having the counter electrode were assembled together by normalprocesses, and a liquid crystal panel was thus obtained. Then, it wasexperimentally confirmed that, similar to Example 1, high-contrastimages could be displayed in transmissive display by using this panel.

Example 6

In Example 6, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 1′ shownin FIGS. 7A to 7C was manufactured.

First, a substrate having TFTs (TFT substrate) similar to that shown inFIG. 26 was formed by processes similar to those of Example 1. Then, analignment film was formed by applying polyimide to a reflectiveelectrode 3 and a transparent electrode 4 provided on the TFT substrateand subjecting it to mask rubbing. In the mask rubbing process, therubbing direction was at an angle of 45° with respect to thetransmission axis of a polarizer 5 to be arranged on the outer side ofthe TFT substrate in the reflective area and was parallel to thetransmission axis of the polarizer 5 in the transmissive area.

Then, a reflective-area λ/4 layer 7 and a counter electrode 8 wereformed on a substrate to face the TFT substrate (counter substrate) byprocesses similar to those of Example 1. An alignment film providedunder the reflective-area λ/4 layer 7 was rubbed in a direction suchthat the slow axis of the reflective-area λ/4 layer 7 was at an angle of45° with respect to the transmission axis of a polarizer 9 to bearranged on the outer side of the counter substrate.

Then, an alignment film was formed on the counter electrode 8 byapplying polyimide on the counter electrode 8 and subjecting it to maskrubbing. In the mask rubbing process, the rubbing direction was at anangle of 90° with respect to the slow axis of the reflective-area λ/4layer 7 in the reflective area and was parallel to the transmission axisof the polarizer 9 in the transmissive area.

The TFT substrate having the alignment film on the display side thereofand the counter substrate were assembled together by normal processes.The TFT substrate and the counter substrate were laminated to each othersuch that the alignment direction of the alignment film on the TFTsubstrate and that of the alignment film on the counter substrate wereantiparallel to each other in the reflective area and were twisted by90° in the transmissive area. Then, a liquid-crystal material whosebirefringence Δn was 0.09 was injected and sealed between thesubstrates, so that a liquid crystal layer 10′ having a phase differenceof λ/4 in the reflective area was obtained. Then, the polarizer 5 wasadhered to the TFT substrate such that the transmission axis thereof wasparallel to the rubbing direction of the alignment film provided on theTFT substrate in the transmissive area. In addition, the polarizer 9 wasadhered to the counter substrate such that the transmission axis thereofwas parallel to the rubbing direction of the alignment film on thecounter substrate in the transmissive area.

Accordingly, a liquid crystal panel whose optical construction was thesame as that of the liquid crystal display 1′ shown in FIGS. 7A to 7Cand which was provided with color filters was thus obtained. Then, itwas experimentally confirmed that the dark state display in transmissivedisplay could be improved compared to the liquid crystal panel ofExample 1 and high-contrast images could be displayed by using thispanel.

Example 7

In Example 7, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 21′shown in FIGS. 10A to 10C was manufactured.

First, a TFT substrate similar to that shown in FIG. 26 was formed byprocesses similar to those of Example 6, and an alignment film wasformed on a reflective electrode 3 and a transparent electrode 4provided on the TFT substrate. The rubbing direction of the alignmentfilm was at an angle of 75° with respect to the transmission axis of apolarizer 5 to be arranged on the outer side of the TFT substrate in thereflective area and was parallel to the transmission axis of thepolarizer 5 in the transmissive area.

Then, a reflective-area λ/2 layer 22 and a reflective-area λ/4 layer 7were formed on a substrate to face the TFT substrate (countersubstrate), and a counter electrode 8 and an alignment film were formedthereon by processes similar to those of Example 2. An alignment filmprovided under the reflective-area λ/4 layer 22 was rubbed in adirection such that the slow axis of the reflective-area λ/2 layer 22was at an angle of 15° with respect to the transmission axis of apolarizer 9 to be arranged on the outer side of the counter substrate,and an alignment film provided under the reflective-area λ/4 layer 7 wasrubbed in a direction such that the slow axis of the reflective-area λ/4layer 7 was at an angle of 60° with respect to the slow axis of thereflective-area λ/2 layer 22 and 75° with respect to the transmissionaxis of the polarizer 9. In addition, the alignment film on the counterelectrode 8 was rubbed in a direction at an angle of 90° with respect tothe slow axis of the reflective-area λ/4 layer 7 and 15° with respect tothe transmission axis of the polarizer 9 in the reflective area, and ina direction parallel to the transmission axis of the polarizer 9 in thetransmissive area.

The TFT substrate having the alignment film on the display side thereofand the counter substrate were assembled together by processes similarto those of Example 6, and a liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 21′shown in FIGS. 10A to 10C and which was provided with color filters wasthus obtained. Then, it was experimentally confirmed that the dark statedisplay in transmissive display could be further improved compared tothe liquid crystal panel of Example 6 and high-contrast images could bedisplayed by using this panel.

Example 8

In Example 8, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 21 ashown in FIGS. 11A to 11C was manufactured.

First, a TFT substrate similar to that shown in FIG. 26 was formed byprocesses similar to those of Example 6, and an alignment film wasformed on a reflective electrode 3 and a transparent electrode 4provided on the TFT substrate. The rubbing direction of the alignmentfilm was at an angle of 52.5° with respect to the transmission axis of apolarizer 5 to be arranged on the outer side of the TFT substrate in thereflective area.

Then, a reflective-area λ/2 layer 22 and a reflective-area λ/4 layer 7were formed on a substrate to face the TFT substrate (countersubstrate), and a counter electrode 8 and an alignment film were formedthereon by processes similar to those of Example 7. The alignment filmwas rubbed in a direction at an angle of 96.5° with respect to the slowaxis of the reflective-area λ/4 layer 7 and 7.5° with respect to thetransmission axis of a polarizer 9 in the reflective area.

The TFT substrate having the alignment film on the display side thereofand the counter substrate were assembled together by normal processes.The TFT substrate and the counter substrate were laminated to each othersuch that the angle between the alignment direction of the alignmentfilm on the TFT substrate and that of the alignment film on the countersubstrate was 45° in the reflective area and 90° in the transmissivearea and the cell gap was 2.7 μm in the reflective area and 4.8 μm inthe transmissive area. Then, a liquid-crystal material whosebirefringence Δn was 0.1 was injected and sealed between the substrates,so that a liquid crystal layer 10′ having a phase difference of λ/4 inthe reflective area was obtained. Then, the polarizer 5 and thepolarizer 9 were adhered in a manner similar to Example 6. A residualphase difference occurred when a voltage was applied was adjusted by theλ/4 layer.

Accordingly, a liquid crystal panel whose optical construction was thesame as that of the liquid crystal display 21 a shown in FIGS. 11A to11C and which was provided with color filters was thus obtained. Then,it was experimentally confirmed that the dark state display could befurther improved compared to the liquid crystal panel of Example 6 andhigh-contrast images could be displayed by using this panel. Inaddition, since the allowance for the cell gap was increased compared tothat in Example 7, the yield of the liquid crystal panel was increased.

Example 9

In Example 9, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 51 shownin FIG. 12 was manufactured.

First, a substrate having TFTs similar to that shown in FIGS. 26 wasformed by processes similar to those of Example 1.

Then, a black matrix composed of Cr was formed on a counter substrate,and red, green, and blue (RGB) filters were formed on the countersubstrate in a predetermined pattern. Then, an alignment film was formedon the color filters by applying polyimide to the color filters byprinting and rubbing it.

In the rubbing process, mask rubbing was performed in which thealignment film was first rubbed in a predetermined direction while oneof a reflective area and a transmissive area was masked with resistusing photolithography techniques, and then rubbed in another directionwhile the other area was masked with resist. The rubbing direction inthe reflective area was at an angle of 45° with respect to thetransmission axis of a polarizer to be arranged on the front, and thatin the transmissive area was parallel to the transmission axis of thepolarizer on the front.

Then, an ultraviolet-curable liquid crystal monomer (RMM 34 produced byMerck Ltd.) was spin-coated on the alignment film and was subjected toan exposure process, so that a λ/4 layer which served as a retardationlayer was formed. The liquid-crystal polymer was aligned along therubbing direction of the alignment film provided under it. Accordingly,although the retardation layer functioned as a λ/4 layer in thereflective area, an effective phase difference did not occur in thetransmissive area since the slow axis thereof was parallel to thetransmission axis of the polarizer on the front. Since thisultraviolet-curable liquid crystal monomer cannot be sufficientlypolymerized when oxygen exists, the above-described processes wereperformed in N₂ atmosphere. In addition, since the birefringence Δn ofRMM 34 is 0.145, the thickness of the retardation layer formed by spincoating was set to 950 nm. Accordingly, the retardation was within therange of 135 nm to 140 nm. After the retardation layer was formed, acounter electrode was formed by sputtering ITO.

Then, normal cell processes were performed. More specifically, analignment film was formed on the counter electrode by applying polyimideto the counter electrode by printing and rubbing it.

The rubbing direction of the alignment film adjacent to the retardationlayer was the same as the orientation of the liquid-crystal polymer onthe side facing the retardation layer. In addition, the rubbingdirection of the alignment film on the substrate having the TFTs was setantiparallel to the rubbing direction of the alignment film adjacent tothe retardation layer.

A liquid-crystal material was injected and sealed between the substratehaving the TFTs and the counter substrate having the retardation layerand the polarizer was laminated on the front such that the slow axis ofthe retardation layer in the transmissive area was parallel to thetransmission axis of the polarizer. Accordingly, a liquid crystal panelwhose optical construction was the same as that of the liquid crystaldisplay shown in FIG. 12 and which was provided with the color filterswas thus obtained. Then, it was experimentally confirmed thathigh-contrast images could be displayed in both reflective display andtransmissive display by using this panel.

Example 10

In Example 10, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 61 shownin FIG. 15 was manufactured.

First, a substrate having TFTs similar to that shown in FIGS. 26 wasformed by processes similar to those of Example 1.

Then, a black matrix composed of Cr was formed on a counter substrate,and red, green, and blue (RGB) filters were formed on the countersubstrate in a predetermined pattern. Then, similar to Example 10, analignment film was formed on the color filters by applying polyimide tothe color filters by printing and rubbing it.

Then, an ultraviolet-curable liquid crystal monomer was spin-coated onthe alignment film and was subjected to an exposure process, so that aλ/2 layer which served as a retardation layer was formed. Theultraviolet-curable liquid crystal monomer was aligned along the rubbingdirection of the alignment film provided under it. Accordingly, althoughthe retardation layer functioned as a λ/2 layer in the reflective area,an effective phase difference did not occur in the transmissive areasince the slow axis of the retardation layer was parallel to thetransmission axis of the polarizer on the front.

Then, polyimide was applied to the λ/2 layer by printing and was rubbedin a direction at an angle of 60° with respect to the rubbing directionof the above-described alignment film in the reflective area and in adirection parallel to the transmission axis of the polarizer on thefront in the transmissive area, so that an alignment film was formed onthe λ/2 layer.

Then, an ultraviolet-curable liquid crystal monomer was applied to thisalignment film and was subjected to an exposure process, so that a λ/4layer which served as a retardation layer was formed. Theultraviolet-curable liquid crystal monomer was aligned along the rubbingdirection of the alignment film provided under it. Accordingly, althoughthe retardation layer functioned as a λ/4 layer in the reflective area,an effective phase difference did not occur in the transmissive areasince the slow axis of the retardation layer was parallel to thetransmission axis of the polarizer on the front.

Then, a counter electrode was formed on the λ/4 layer by sputtering ITO.

Then, normal cell processes were performed. More specifically, analignment film was formed on the counter electrode by applying polyimideto the counter electrode by printing and rubbing it. The rubbing processwas performed such that the orientation of the liquid-crystal layer isbetween λ/2 and λ/4.

The substrate having the TFTs and the counter substrate having theretardation layer were assembled together by normal processes, and thepolarizers were laminated on the outer sides of the substrates. Thepolarizer on the front was arranged such that the transmission axisthereof was at an angle of 15° with respect to the slow axis of thereflective-area λ/2 layer, and the polarizer on the back was arrangedsuch that the transmission axis thereof was at an angle of 90° withrespect to the transmission axis of the polarizer on the front.Accordingly, the slow axis of the reflective-area λ/2 layer was parallelto the transmission axis of the polarizer on the front.

Accordingly, a liquid crystal panel whose optical construction was thesame as that of the liquid crystal display shown in FIG. 15 and whichwas provided with the color filters was thus obtained. Then, it wasexperimentally confirmed that high-contrast images could be displayed inboth reflective display and transmissive display by using this panel.

Example 11

In Example 11, a liquid crystal panel whose optical construction was thesame as that of the liquid crystal display 71 shown in FIG. 16 wasmanufactured.

First, a substrate having TFTs similar to that shown in FIG. 26 wasformed by processes similar to those of Example 1. Then, an λ/4 layerwhich served as a retardation layer was formed on a reflective electrodeand a transparent electrode provided on the substrate by applying anultraviolet-curable liquid crystal monomer. In this process, in orderfor the retardation layer to function as a λ/4 layer only in thereflective area, an underlayer thereof was subjected to mask rubbingsuch that the rubbing direction differs between the reflective area andthe transmissive area. Then, an alignment film was formed on theretardation layer by applying polyimide to the retardation layer byprinting.

In addition, a counter electrode was formed on a counter substrate bysputtering ITO, and no retardation layer was formed on this substrate.Then, an alignment film was formed on the counter electrode by applyingpolyimide to the counter electrode by printing and rubbing it.

The substrate having the TFTs and the retardation layer and the countersubstrate having the counter electrode were assembled together by normalprocesses, and a liquid crystal panel was thus obtained. Then, it wasexperimentally confirmed that, similar to Example 9, high-contrastimages could be displayed in transmissive display by using this panel.

Example 12

In Example 12, a liquid crystal display whose optical construction wasthe same as that of the liquid crystal display 81 shown in FIG. 17 wasmanufactured.

First, a substrate having TFTs similar to that shown in FIG. 26 wasformed by processes similar to those of Example 1.

Then, a black matrix composed of Cr was formed on a counter substrate,and red, green, and blue (RGB) filters were formed on the countersubstrate in a predetermined pattern. Then, similar to Example 9, analignment film was formed on the color filters by applying polyimide tothe color filters by printing and rubbing it.

Then, an ultraviolet-curable liquid crystal monomer was applied to thealignment film and was subjected to an exposure process so that α/4layers which served as retardation layers was formed. The thickness ofeach retardation layer was set in accordance with a phase difference ofits corresponding pixel. More specifically, the thickness of theretardation layer for a green pixel was set to 950 nm as in Example 1.In addition, the thickness of the retardation layer for a blue pixel wasset to 730 nm since the birefringence Δn was about 0.155 according tothe retardation at the blue pixel, and the thickness of the retardationlayer for a red pixel was set to 1200 nm since the birefringence Δn wasabout 0.135 according to the retardation at the red pixel.

The ultraviolet-curable liquid crystal monomer was aligned along therubbing direction of the alignment film provided under it. Accordingly,although the retardation layers functioned as a λ/4 layer in thereflective area, an effective phase difference did not occur in thetransmissive area since the slow axes of the retardation layers wereparallel to the transmission axis of the polarizer on the front.

After the retardation layers were formed, a counter electrode was formedby sputtering ITO.

The substrate having the TFTs and the substrate having the retardationlayer were assembled together by normal processes, and a liquid crystalpanel whose optical construction was the same as that of the liquidcrystal display 81 shown in FIG. 17 was thus obtained. Then, it wasexperimentally confirmed that the dark state display could be improvedcompared to the liquid crystal panel of Example 9 and high-contrastimages could be displayed by using this panel.

Example 13

In Example 13, a full-color liquid crystal panel was manufacturedsimilarly to that of Example 10 except that multi-domain alignment ofthe retardation layer was achieved by a photoalignment process. InExample 13, an alignment film was formed by using a material produced byVantico Inc.

It was experimentally confirmed that, similar to Example 10,high-contrast images could be displayed in both reflective display andtransmissive display by using this panel.

Example 14

In Example 14, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 51′shown in FIGS. 18A to 18C was manufactured.

First, a substrate having TFTs (TFT substrate) similar to that shown inFIGS. 26 was formed by processes similar to those of Example 1. In thisExample, an interlayer film 52 having a thickness corresponding to thedifference between the cell gap in the reflective area and that in thetransmissive area was provided under a reflective electrode 3 providedon the TFT substrate.

Then, an alignment film 53 was formed by applying polyimide to thereflective electrode 3 and a transparent electrode 4 provided on the TFTsubstrate and subjecting it to mask rubbing. In the mask rubbingprocess, the rubbing direction was at an angle of 45° with respect tothe transmission axis of a polarizer 5 to be arranged on the outer sideof the TFT substrate in the reflective area and was parallel to thetransmission axis of the polarizer 5 in the transmissive area.

Then, a reflective-area λ/4 layer 7, a transmissive-area λ/4 layer 55,and a counter electrode 8 were formed on a substrate to face the TFTsubstrate (counter substrate) by processes similar to those of Example9. The slow axis of the reflective-area λ/4 layer 7 was set at an angleof 45° with respect to the transmission axis of a polarizer 9 to bearranged on the counter substrate, and the slow axis of thetransmissive-area λ/4 layer 55 was set parallel to the transmission axisof the polarizer 9.

Then, an alignment film 56 was formed on the counter electrode 8 byapplying polyimide on the counter electrode 8 and performing maskrubbing such that the rubbing direction was at an angle of 90° withrespect to the slow axis of the reflective-area λ/4 layer 7 in thereflective area and was parallel to the slow axis of thetransmissive-area λ/4 layer 55.

The TFT substrate having the alignment film 53 on the display sidethereof and the counter substrate were assembled together by normalprocesses. The TFT substrate and the counter substrate were laminated toeach other such that the alignment direction of the alignment film 53 onthe TFT substrate and that of the alignment film 56 on the countersubstrate were antiparallel to each other in the reflective area andwere at an angle of 90° to each other in the transmissive area and thecell gap was 1.4 μm in the reflective area and 4.0 μm in thetransmissive area. Then, a liquid-crystal material whose birefringenceΔn was 0.12 was injected and sealed between the substrates, so that aliquid crystal layer 10′ having a phase difference of μ/4 in thereflective area was obtained. Then, the polarizer 5 was adhered to theTFT substrate such that the transmission axis thereof was parallel tothe rubbing direction of the alignment film 53 in the transmissive area.In addition, the polarizer 9 was adhered to the counter substrate suchthat the transmission axis thereof was parallel to the rubbing directionof the alignment film 56 in the transmissive area. A residual phasedifference occurred when a voltage was applied was adjusted by the λ/4layer.

Accordingly, a liquid crystal panel whose optical construction was thesame as that of the liquid crystal display 51′ shown in FIGS. 18A to 18Cand which was provided with color filters was thus obtained. Then, itwas experimentally confirmed that high-contrast images could bedisplayed in both reflective display in the reflective area andtransmissive display in the transmissive area by using this panel. Inparticular, in transmissive display, the contrast was higher than thatobtained in Example 9 (see FIG. 12), and the viewing angle wasincreased.

In Example 14, another liquid crystal panel including a liquid crystallayer 10′ which had a phase difference of λ/4 in the reflective area wasobtained by laminating a TFT substrate and a counter substrate to eachother such that the cell gap was 1.8 μm in the reflective area and 4.8μm in the transmissive area and injecting and sealing a liquid-crystalmaterial whose birefringence Δn was 0.01. As a result, similar effectswere also obtained by this panel. Also in this case, a residual phasedifference occurred when a voltage was applied was adjusted by the λ/4layer.

Example 15

In Example 15, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 61′shown in FIGS. 21A to 21C was manufactured.

First, a substrate having TFTs and an interlayer film 52 (TFT substrate)similar to that shown in FIGS. 26 was formed by processes similar tothose of Example 14, and an alignment film 53 was formed on a reflectiveelectrode 3 and a transparent electrode 4 provided on the TFT substrate.The rubbing direction of the alignment film 53 was at an angle of 15°with respect to the transmission axis of a polarizer 5 to be arranged onthe outer side of the TFT substrate in the reflective area and wasparallel to the transmission axis of the polarizer 5 in the transmissivearea.

Then, a reflective-area λ/2 layer 22, a reflective-area λ/4 layer 7, atransmissive-portion λ/2 layer 62, and a transmissive-area λ/4 layer 55were formed on a substrate to face the TFT substrate (countersubstrate), and a counter electrode 8 and an alignment film 56 wereformed thereon by processes similar to those of Example 10. An alignmentfilm provided under the reflective-area λ/4 layer 22 was rubbed in adirection such that the slow axis of the reflective-area λ/2 layer 22was at an angle of 75° with respect to the transmission axis of apolarizer 9 to be arranged on the outer side of the counter substrate.In addition, an alignment film provided under the reflective-area λ/4layer 7 was rubbed in a direction such that the slow axis of thereflective-area λ/4 layer 7 was at an angle of 60° with respect to theslow axis of the reflective-area λ/2 layer 22 and 15° with respect tothe transmission axis of the polarizer 9. In addition, alignment filmsunder the transmissive-portion λ/2 layer 62 and the transmissive-areaλ/4 layer 55 were rubbed in directions such that the slow axes of thetransmissive-portion λ/2 layer 62 and the transmissive-area λ/4 layer 55were parallel to the transmission axis of the polarizer 9. In addition,the alignment film 56 was rubbed in a direction at an angle of 90° withrespect to the slow axis of the reflective-area λ/4 layer 7 and 75° withrespect to the transmission axis of the polarizer 9 in the reflectivearea, and in a direction parallel to the transmission axis of thepolarizer 9 in the transmissive area.

The TFT substrate and the counter substrate having the alignment films53 and 56, respectively, were assembled together by processes similar tothose of Example 14, and a liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 61′shown in FIGS. 21A to 21C was thus obtained. Then, it was experimentallyconfirmed that high-contrast images could be displayed in bothreflective display in the reflective area and transmissive display inthe transmissive area by using this panel. In particular, in reflectivedisplay, the contrast was higher than that obtained in Example 14. Inaddition, in transmissive display, high contrast was obtained and theviewing angle was increased similar to Example 14.

Example 16

In Example 16, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 71′shown in FIG. 22 was manufactured. This panel had the same opticalconstruction as that of the liquid crystal panel of Example 14 which isdescribed above with reference to FIGS. 18A to 18C, and was differentfrom the panel of Example 14 in that the retardation layers wereprovided on the TFT substrate.

First, a substrate having TFTs and an interlayer film 52 (TFT substrate)similar to that shown in FIG. 26 was obtained by processes similar tothose of Example 11. Then, a reflective-area λ/4 layer 7 and atransmissive-area λ/4 layer 55 were formed on a reflective electrode 3and a transparent electrode 4, respectively, which were provided on theTFT substrate, and an alignment film 53 was formed on thereflective-area λ/4 layer 7 and the transmissive-area λ/4 layer 55. Therubbing direction of the alignment film 53 was at an angle of 45° withrespect to the transmission axis of a polarizer 5 to be arranged on theouter side of the TFT substrate in the reflective area and was parallelto the transmission axis of the polarizer 5 in the transmissive area.

Then, an interlayer film 52 having a thickness corresponding to thedifference between the cell gap in the reflective area and that in thetransmissive area was formed on a substrate to face the TFT substrate(counter substrate) in the reflective area by processes similar to thoseof Example 11. Then, a counter electrode 8 and an alignment film 56 wereformed on the counter substrate. The rubbing direction of the alignmentfilm 56 was at an angle of 45° with respect to the transmission axis ofa polarizer 9 provided on the outer side of the counter substrate andwas antiparallel with respect to the rubbing direction of the alignmentfilm 53 on the TFT substrate in the reflective area, and was parallel tothe transmission axis of the polarizer 9 in the transmissive area.

The TFT substrate and the counter substrate having the alignment films53 and 56, respectively, were assembled together by processes similar tothose of Example 14, and a liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 71′shown in FIG. 22 was thus obtained. Then, it was experimentallyconfirmed that, similar to Example 14, high-contrast images could bedisplayed in both reflective display in the reflective area andtransmissive display in the transmissive area by using this panel.

Example 17

In Example 17, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 80′shown in FIG. 23 was manufactured.

First, a substrate having TFTs (TFT substrate) similar to that shown inFIGS. 26 was formed by processes similar to those of Example 1. In thisExample, an interlayer film 52 having a thickness corresponding to thedifference between the cell gap in the reflective area and that in thetransmissive area was provided under a reflective electrode 3 providedon the TFT substrate shown in FIG. 26.

Then, an alignment film 53 was formed by applying polyimide to thereflective electrode 3 and a transparent electrode 4 provided on the TFTsubstrate and subjecting it to mask rubbing. In the mask rubbingprocess, the rubbing direction was at an angle of 45° with respect tothe transmission axis of a polarizer 5 to be arranged on the outer sideof the TFT substrate in the reflective area and was parallel to thetransmission axis of the polarizer 5 in the transmissive area.

Then, red, green, and blue (RGB) filters 42R, 42Q and 42B were formed ona substrate to face the TFT substrate (counter substrate) by processessimilar to those of Example 12 (see FIG. 17), and reflective-area λ/4layers 7R, 7C; and 7B and transmissive-area λ/4 layers 55R, 55C; and 55Bwhose thicknesses were set in accordance with the retardation of theirrespective colors were formed on the color filters 42R, 42Q, and 42B,respectively. Then, an alignment film 56 was formed on thereflective-area λ/4 layers 7R, 7G, and 7B and the transmissive-area λ/4layers 55R, 55C; and 55B with an overcoat layer 43 and a counterelectrode 8 therebetween. The slow axes of the reflective-area λ/4layers 7R, 7G, and 7B were at an angle of 45° with respect to thetransmission axis of a polarizer 9 to be arranged on the outer side ofthe counter electrode, and those of the transmissive-area λ/4 layers55R, 55C; and 55B were set parallel to the transmission axis of thepolarizer 9. In addition, the alignment film 56 was rubbed in adirection at an angle of 90° with respect to the slow axes of thereflective-area λ/4 layers 7R, 7Q and 7B in the reflective area and in adirection parallel to the slow axes of the transmissive-area λ/4 layers55R, 55G, and 55B in the transmissive area. The optical axes and therubbing directions were the same as those in the liquid crystal panel ofExample 14 which is described above with reference to FIG. 18. Inaddition, the thicknesses of the retardation layers were set inaccordance with the retardation of their respective colors.

The TFT substrate and the counter substrate having the alignment films53 and 56, respectively, were assembled together by processes similar tothose of Example 14, and a liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 81′shown in FIG. 23. Then, it was experimentally confirmed that the darkstate display could be improved compared to Example 14 and high-contrastimages could be displayed in both reflective display in the reflectivearea and transmissive display in the transmissive area by using thispanel.

Example 18

In Example 18, a full-color liquid crystal panel was manufacturedsimilarly to that of Example 15 except that multi-domain alignment foraligning the retardation layer in different directions between thereflective area and the transmissive area was achieved by aphotoalignment process. In the photoalignment process, the transmissivearea and the reflective area were irradiated with light of differentpolarizations by mask exposure, so that the reflective-area λ/4 layerand the transmissive-area λ/4 layer were aligned in directions similarto those in Example 18.

It was experimentally confirmed that, similar to Example 15,high-contrast images could be displayed in both reflective display andtransmissive display by using this panel.

Example 19

In Example 19, a full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 61 ashown in FIGS. 24A to 24C was manufactured.

First, a substrate having TFTs and an interlayer film 52 (TFT substrate)similar to that shown in FIGS. 26 was formed by processes similar tothose of Example 14, and an alignment film 53 was formed on a reflectiveelectrode 3 and a transparent electrode 4 provided on the TFT substrate.The rubbing direction of the alignment film 53 was at an angle of 37.5°with respect to the transmission axis of a polarizer 5 to be arranged onthe outer side of the TFT substrate in the reflective area and wasparallel to the transmission axis of the polarizer 5 in the transmissivearea.

Then, a reflective-area λ/2 layer 22, a reflective-area λ/4 layer 7, atransmissive-portion λ/2 layer 62, and a transmissive-area λ/4 layer 55were formed on a substrate to face the TFT substrate (countersubstrate), and a counter electrode 8 and an alignment film 56 wereformed thereon by processes similar to those of Example 15 (see FIG.21C). The alignment film 56 was rubbed in a direction at an angle of22.5° with respect to the slow axis of the reflective-area λ/4 layer 7in the reflective area and in a direction parallel to the transmissionaxis of a polarizer 9 in the transmissive area.

The TFT substrate and the counter substrate having the alignment films53 and 56, respectively, were assembled together by processes similar tothose of Example 14. The TFT substrate and the counter substrate werelaminated to each other such that the angle between the rubbingdirections of the alignment films 53 and 56 was 45° in the reflectivearea and 90° in the transmissive area and the cell gap was 2.7 μm in thereflective area and 4.8 μm in the transmissive area. Then, aliquid-crystal material whose birefringence Δn was 0.10 was injected andsealed between the substrates. Then, the polarizer 5 was adhered to theTFT substrate such that the transmission axis thereof was parallel tothe rubbing direction of the alignment film 53 in the transmissive area.In addition, the polarizer 9 was adhered to the counter substrate suchthat the transmission axis thereof was parallel to the rubbing directionof the alignment film 56 in the transmissive area.

Accordingly, a liquid crystal panel whose optical construction was thesame as that of the liquid crystal display 61 a shown in FIGS. 24A to24C and which was provided with color filters was thus obtained. Then,it was experimentally confirmed that, similar to Example 15,high-contrast images could be displayed in both reflective display inthe reflective area and transmissive display in the transmissive area byusing this panel. In addition, since the liquid crystal layer in thereflective area was in the twisted nematic state and the allowance forthe cell gap was increased compared to that in Example 15, the yield ofthe liquid crystal panel was increased.

In Example 19, another full-color liquid crystal panel whose opticalconstruction was the same as that of the liquid crystal display 61 ashown in FIGS. 25A to 25C was obtained by laminating a TFT substrate anda counter substrate to each other such that the angle between thealignment direction of the alignment film 53 on the TFT substrate andthat of the alignment film 56 on the counter electrode was 90° in boththe reflective and transmissive areas and the cell gap was 3.3 μm in thereflective area and 4.8 μm in the transmissive area and injecting andsealing a liquid-crystal material whose birefringence Δn was 0.10. As aresult, similar effects were also obtained by this panel.

1. A liquid crystal display comprising: a pair of substrates; and aliquid crystal layer interposed between the substrates, wherein theliquid crystal display has a reflective area and a transmissive area,wherein at least one of the substrates is provided with a retardationfilm whose phase difference differs between the reflective area and thetransmissive area, and wherein the liquid crystal layer has a phasedifference of λ/4 in the reflective area and is in a 90° twisted nematicstate in the transmissive area when no voltage is applied or when avoltage is applied.
 2. A liquid crystal display according to claim 1,wherein the liquid crystal layer is in a twisted nematic state in thereflective area when no voltage is applied or when a voltage is applied.3. A liquid crystal display according to claim 1, wherein the liquidcrystal layer displays an image in an electrically controlledbirefringence mode in the reflective area and in a twisted nematic modein the transmissive area.
 4. A method for manufacturing a liquid crystaldisplay which has a pair of substrates and a liquid crystal layerinterposed between the substrates and which has a reflective area and atransmissive area, the method comprising the steps of: forming aretardation film on at least one of the substrates; patterning theretardation film such that the retardation film remains at least in thereflective area and the phase difference of the retardation film differsbetween the reflective area and the transmissive area, and furthercomprising the step of forming an alignment film by photoalignment suchthat the alignment direction of the alignment film differs between thereflective area and the transmissive area on a surface of at least oneof the substrates which faces the liquid crystal layer.
 5. A liquidcrystal display comprising: a pair of substrates; and a liquid crystallayer interposed between the substrates, wherein the liquid crystaldisplay has a reflective area and a transmissive area, and wherein atleast one of the substrates is provided with a retardation film whoseslow axis differs between the reflective area and the transmissive area.6. A liquid crystal display according to claim 5, wherein theretardation film is provided on a surface of the substrate which facesthe liquid crystal layer.
 7. A liquid crystal display according to claim5, wherein a polarizer is provided on at least one of the substrates andthe slow axis of the retardation film in the transmissive area isparallel to the transmission axis or the absorption axis of thepolarizer.
 8. A liquid crystal display according to claim 5, wherein apolarizer is provided on at least one of the substrates and theretardation layer polarizes light incident from the liquid crystal layerin a direction parallel to the absorption axis of the polarizer in thetransmissive area when no voltage is applied or when a voltage isapplied.
 9. A liquid crystal display according to claim 5, wherein theretardation film comprises a λ/4 layer.
 10. A liquid crystal displayaccording to claim 9, wherein the retardation film comprises a λ/4 layerand a retardation layer which compensates for chromatic dispersion whichoccurs at the λ/4 layer.
 11. A liquid crystal display according to claim10, wherein the retardation layer comprises a λ/2 layer.
 12. A liquidcrystal display according to claim 5, wherein at least one of thesubstrates is provided with color filters and the phase difference ofthe retardation film is determined in accordance with the wavelength ofeach color filter.
 13. A liquid crystal display according to claim 12,wherein the retardation film has a phase difference of λ/4 in accordancewith the wavelength of each color filter.
 14. A liquid crystal displayaccording to claim 5, wherein the liquid crystal layer has a phasedifference of λ/4, where λ is the wavelength of light, in the reflectivearea and a phase difference of λ/2 in the transmissive area when novoltage is applied or when a voltage is applied.
 15. A liquid crystaldisplay according to claim 5, wherein the liquid crystal layer has aphase difference of λ/4, where λ is the wavelength of light, in thereflective area and is in a 90° twisted nematic state in thetransmissive area when no voltage is applied or when a voltage isapplied.
 16. A liquid crystal display according to claim 15, wherein theliquid crystal layer is in a twisted nematic state in the reflectivearea when no voltage is applied or when a voltage is applied.
 17. Aliquid crystal display according to claim 15, wherein the liquid crystallayer displays an image in an electrically controlled birefringence modein the reflective area, and in a twisted nematic mode in thetransmissive area.
 18. A liquid crystal display according to claim 5,wherein the retardation film is composed of a liquid crystal polymer.19. A liquid crystal display according to claim 18, wherein the liquidcrystal polymer is obtained by curing an ultraviolet-curable liquidcrystal monomer in a nematic phase.
 20. A method for manufacturing aliquid crystal display which has a pair of substrates and a liquidcrystal layer interposed between the substrates and which has areflective area and a transmissive area, the method comprising the stepof: forming a retardation film whose slow axis is different between thereflective area and the transmissive area on at least one of thesubstrates.
 21. A method for manufacturing a liquid crystal displayaccording to claim 20, wherein the retardation film is composed of aliquid crystal polymer.
 22. A method for manufacturing a liquid crystaldisplay according to claim 21, wherein the liquid crystal polymer isobtained by curing an ultraviolet-curable liquid crystal monomer in anematic phase.
 23. A method for manufacturing a liquid crystal displayaccording to claim 20, wherein the retardation film is formed by formingan alignment film by mask rubbing such that the alignment direction ofthe alignment film differs between the reflective area and thetransmissive area, and applying a liquid crystal polymer or anultraviolet-curable liquid crystal monomer in a nematic phase on thealignment film.
 24. A method for manufacturing a liquid crystal displayaccording to claim 20, wherein the retardation film is formed by formingan alignment film by photoalignment such that the alignment direction ofthe alignment film differs between the reflective area and thetransmissive area, and applying a liquid crystal polymer or anultraviolet-curable liquid crystal monomer in a nematic phase on thealignment film.
 25. A method for manufacturing a liquid crystal displayaccording to claim 20, further comprising the step of forming analignment film by mask rubbing such that the alignment direction of thealignment film differs between the reflective area and the transmissivearea on a surface of at least one of the substrates which faces theliquid crystal layer.
 26. A method for manufacturing a liquid crystaldisplay according to claim 20, further comprising the step of forming analignment film by photoalignment such that the alignment direction ofthe alignment film differs between the reflective area and thetransmissive area on a surface of at least one of the substrates whichfaces the liquid crystal layer.